Re: Copy an Object (Again?)

[Schüle Daniel]

KraftDiner wrote:
> I'm having trouble getting a copy of and object... (a deep copy)
> 
> I'm writing a method that creates a mirror image of an object (on
> screen)
> In order to do this i need to get a copy of the object and then modify
> some
> of its attributes.
> 
> I tried:
> objs = myListOfObjects
> for obj in objs:
>if obj.flag:
>   newObject = copy.deepcopy(obj)
>   newObject.mirror()
>   myListOfObjects.append(newObject)
> 
> That doesn't seem to work.. the new object seems to disapear from
> existance.
> I'm wondering if its a bug in my application or if this is my shallow
> understanding of the language.
> 
> TIA
> B.
> 

I think you should provide more code, eg what attributes does your 
object have?
imagine the situation like this

 >>> import copy
 >>> class A:
... lst=[1, 2, 3]
...
 >>> a=A()
 >>> b=copy.deepcopy(a)
 >>> a
<__main__.A instance at 0x403e3c8c>
 >>> a.lst
[1, 2, 3]
 >>> b.lst
[1, 2, 3]
 >>> b.lst.append(4)
 >>> b.lst
[1, 2, 3, 4]
 >>> a.lst
[1, 2, 3, 4]

or even if you "could" copy instances

class X:
def __init__(self, filename = "/path/file")
self.file = file(filename, "w+")
def modifyByteAt(offset):
self.file.tell(offset)
self.file.write("X")

this is untested pseudocode, it should only give you an idea

hth, Daniel

ps:
question to all
what is a general approach to copy class instances?
write own method or is there some __magic__ attribute or
should one use pickle.dump?

Regards, Daniel

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Re: Copy an Object (Again?)

[Schüle Daniel]

I was not very clear about it

> or even if you "could" copy instances
> 
> class X:
> def __init__(self, filename = "/path/file")
> self.file = file(filename, "w+")
> def modifyByteAt(offset):
> self.file.tell(offset)
> self.file.write("X")
> 
> this is untested pseudocode, it should only give you an idea

even when x=X() and y=copyItSomehowFrom(x)
what is supposed to be copied?
the whole file? but where?

in your case .. what is supposed to happen with the mirrored image?
should it be mirrored inplace
if I recall properly in "import PIL.Image as image" if you image.open
an image and want to mirror it you can create a real copy
and then "save as " it into a file

my 2 cents

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decorator question

[Schüle Daniel]

hello NG,

consider this code

 >>> def timelogger(f):
... def wrapper(*a,**kw):
... print "started at %s" % time.ctime()
... t0 = time.time()
... f(*a, **kw)
... t1 = time.time()
... print "ended at %s" % time.ctime()
... print "diff = ", t1-t0, "sec"
... return wrapper
...
 >>> import time
 >>> @timelogger
... def loops(a,b,c):
... sum = 0
... for i in range(a):
... for j in range(b):
... for k in range(c):
... sum += 1
...
 >>> loops

 >>> loops(10,10,10)
started at Sun Jan  8 23:19:19 2006
ended at Sun Jan  8 23:19:19 2006
diff =  0.000367164611816 sec

the code above works fine
but I am wondering wheather it's possible to
write something like this

 >>> def timelogger(f, logfile=sys.stdout):
... def wrapper(*a,**kw):
... logfile.write("started at %s" % time.ctime())
... t0 = time.time()
... f(*a, **kw)
... t1 = time.time()
... logfile.write("ended at %s" % time.ctime())
... logfile.write("diff = %f %s" % (t1-t0, "sec"))
... return wrapper

 >>> import time
 >>> @timelogger(file("hierher", "a"))  ### << (1)
... def loops(a,b,c):
... sum = 0
... for i in range(a):
... for j in range(b):
... for k in range(c):
... sum += 1
...

(1) fails to compile
is it possible to pass parameters to a decorator function?

Regards, Daniel

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Re: decorator question

[Schüle Daniel]

thx to all

now I understand how it works and why it should be done in this way
so it's possible to write more than only one declarator

 >>> def foo(f):
... l = [1]
... def method(*a,**kw):
... f(l, *a, **kw)
... return method
...
 >>> def bar(f):
... l = [2]
... def method(*a,**kw):
... f(l, *a, **kw)
... return method
...
 >>> @foo
... @bar
... def foobar(x,y,z):
... print x
... print y
... print z
...
 >>> foobar(1)
[2]
[1]
1

x and y are already binded
by the way .. to l's lists are considered to be in closure?
Or what is the right denotation for them?
Can someone give me some pointers to the metaprogramming in Python?
links etc

Regards, Daniel

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rational numbers

[Schüle Daniel]

Hello NG,

recently I was using Scheme and Ruby and was really nicely surprised
to find there support for the computing with rational numbers

for example this how it works in Ruby

mond:/pool/PROG/ruby # irb
irb(main):001:0>
irb(main):002:0* require "mathn"
=> true
irb(main):003:0> r = Rational(1,3)
=> 1/3
irb(main):004:0> p = Rational(1,5)
=> 1/5
irb(main):005:0> r+p
=> 8/15
irb(main):007:0> (r+p)**2
=> 64/225
irb(main):008:0>

does anybody know modules which make rational numbers available?
and are there considerations to add them to the core, like
complex numbers (maybe in Python 3)

Regards, Daniel

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Re: simple question

[Schüle Daniel]

Steve Holden schrieb:
> Maxine Weill wrote:
>> I need to install Python Imaging Library (PIL) - imaging-1.1.5.tar.gz 
>> (source ) onto Suse Linux 10.1 system in order for (latest) Scribus 
>> 1.3.3.2  to install and work.
>>
>> Plesae indicate how I perform PIL install (exact commands/procedures)  
>> in manner where files are "automatically" placed in proper 
>> directories, etc.
>>
> 
> I though that PIL now used the standard setup system. If the package's 
> top level directory includes a file called "setup.py" then just run
> 
> python setup.py install

if there are more versions of python installed
and one wants to install for specific version then
/pool/pathToMyInstalledSoftware/bin/python2.4 setup.py install
/pool/pathToPetersInstalledSoftware/bin/python2.2 setup.py install

this is what I figured out

my 2 cents
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self question

[Schüle Daniel]

Hi all,

given python description below

import random

class Node:
 def __init__(self):
 self.nachbarn = []

class Graph(object):
# more code here
 def randomizeEdges(self, low=1, high=self.n):
 pass


graph = Graph(20)
graph.randomizeEdges(2,5)

I am burned by high=self.n
quick test with

cnt = 1
def foo():
global cnt
cnt += 1
return cnt

def bar(x=foo()):
print x

bar()   # 2
bar()   # 2
bar()   # 2

this is not behaviour C++ programmer would expect
does someone know why this kind of behaviour is/was choosen?

Regards, Daniel
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Re: self question

[Schüle Daniel]

[EMAIL PROTECTED] schrieb:
>> cnt = 1
>> def foo():
>>  global cnt
>>  cnt += 1
>>  return cnt
>>
>> def bar(x=foo()):
>>  print x
>>
>> bar()# 2
>> bar()# 2
>> bar()# 2
> 
> Looks to me like you want to use the following programming pattern to
> get dynamic default arguments:
> 
> cnt = 1
> def foo():
>   global cnt
>   cnt += 1
>   return cnt
> 
> def bar(x=None):
>   if x is None:
>   x = foo()
>   print x
>  
> bar() # 2
> bar() # 3
> bar() # 4

yes, I haven't thought of that
nowI changed my class to

class Graph:
settings = {
"NumNodes" : 10,
"MinNodes" : 2,
"MaxNodes" : 5
}
def randomizeEdges(self,
lowhigh = (settings["MinNodes"], settings["MaxNodes"])):
low, high = lowhigh
for node in self.nodes:
x = random.randint(low, high)
# link the nodes


maybe the only minor point is that no relationship
can be expressed

settings = {
"NumNode" : 10,
"MinNode" : settings["NumNode"] / 2,
"MaxNode" : settings["NumNode"]
}

but I think the solution is nevertheless ok


Regards, Daniel
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Re: self question

[Schüle Daniel]

correction :)

> class Graph:
> settings = {
> "NumNodes" : 10,
> "MinNodes" : 2,
> "MaxNodes" : 5
> }
> def randomizeEdges(self,
> lowhigh = (settings["MinNodes"], settings["MaxNodes"])):

of course this should be
  Graph.settings["MinNodes"], Graph.settings["MaxNodes"])
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basic questions on cmp, < and sort

[Schüle Daniel]

Hello,

first question

In [117]: cmp("ABC",['A','B','C'])
Out[117]: 1

against what part of the list is the string "ABC" compared?

second question

In [119]: class X(object):
.: pass
.:

In [120]: X() < X()
Out[120]: True

In [121]: X() < X()
Out[121]: False

In [122]: X() < X()
Out[122]: True

In [123]: X() < X()
Out[123]: True

In [124]: X() < X()
Out[124]: False

class X does not implement < and cmp
what is this comparision is based on?

third question

sort([[1,2,3],["ABC"],['Z','A'], X(), 4)

how does python handle heterogenous items in the list
in this case?

first I assumed that cmp function used in sort
is based on len, when the items are sequences, but this is wrong

Regards, Daniel
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re question

[Schüle Daniel]

Hello all,

I didn't found more appropriate news group for
this question, please let me know if there is ng with
regular expression as its main topic

I am trying to construct a case where a greedy and
non greedy operation produce different result.
I dont see the difference between 'a??b' and 'a?b'
As far I understand is that ? will first try to match a
(it's greedy) and only if it fails then it step back
and lets a unmatched. The other doesn't match a at first,
only if the pattern fails to match it steps back and match a.

But don't they do eventually the same thing?
Can someone provide an example where 2 patterns yield
different results.

Regards, Daniel
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Re: integer to binary...

[Schüle Daniel]

[EMAIL PROTECTED] schrieb:
> does anyone know a module or something to convert numbers like integer
> to binary format ?

unfortunately there is no builtin function for this

 >>> int("111",2)
7
 >>> str(7)
'7'
 >>> str(7,2)
Traceback (most recent call last):
   File "", line 1, in ?
TypeError: str() takes at most 1 argument (2 given)
 >>>

int, str are not symmetrical
I hope this will change in future



you can use Ruby's 7.to_s(2) for this
irb(main):001:0> 7.to_s(2)
=> "111"
irb(main):002:0> 7.to_s(3)
=> "21"
irb(main):003:0>



> for example I want to convert number 7 to 0111 so I can make some
> bitwise operations...

you can use bitwise operations on int's anyway

7 & 3 == 3
(1 << 20) | (1 << 10) == 2**20+2**10

and so on
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Re: beginner code problem

[Schüle Daniel]

Hello

> Here's the code I wrote:
> 
> import random
> 
> flip = random.randrange(2)
> heads = 0
> tails = 0
> count = 0
> 
> while count < 100:
> 
> if flip == 0:

flip never changes again
it's not reassigned in the while loop

> heads += 1
> 
> else:
> tails += 1
> 
> 
> count += 1
> 
> 
> 
> print "The coin landed on heads", heads, 'times ' \
> "and tails", tails, 'times'
> 


in case you know how many times to iterate
it's better to use for loop (in python and eq C also)

from random import randrange as flip
result = [0,0]
for i in range(100):
result[flip(2)] += 1

or

from random import randrange as flip
result = {"head":0,
  "tail":0}
for i in range(100):
result[["head","tail"]flip(2)] += 1

or

 >>> class Coin:
... def flip(self):
... import random
... return ("head", "tail")[random.randrange(2)]
c = Coin()
result = {"head":0,"tail":0}
for i in range(100):
result[c.flip()] += 1

or many many more
the important thing is .. to know what is the
most suitable data representation for you

is it throw-away-code or is this going to be read
by other people .. etc

hth, Daniel
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Re: Importing again and again

[Schüle Daniel]

it's import-ed only once

# magic.py file

#!/usr/bin/python
print "here"
import magic# try to import itself

then try

# bad_magic.py

#!/usr/bin/python
print "here"
import bad_magic
reload(bad_magic)


hth, Daniel
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Re: @func call syntax

[Schüle Daniel]

this is decorator, this is how it's may be implented

 >>> def returns(t):
... def dec(f):
... def wrapped(*args, **kwargs):
... ret = f(*args, **kwargs)
... assert type(ret) is t
... return ret
... return wrapped
... return dec
...
 >>>
 >>> @returns(int)
... def f1():
... return 1
...
 >>> @returns(float)
... def f2():
... return 2.0
...
 >>> @returns(str)
... def f3():
... return 1
...
 >>> f1()
1
 >>> f2()
2.0
 >>> f3()
Traceback (most recent call last):
   File "", line 1, in ?
   File "", line 5, in wrapped
AssertionError
 >>>


I can imagine that stuff like this may be extremely usefull
when testing you program
later one could parse and remove all such assertations
easy and cut them all at once

Regards, Daniel
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Re: for and while loops

[Schüle Daniel]

[EMAIL PROTECTED] schrieb:
> i was wondering if anyone could point me to some good reading about the
> for and while loops
> 
> i am trying to write some programs
> "Exercise 1
> 
> Write a program that continually reads in numbers from the user and
> adds them together until the sum reaches 100. Write another program

the hidden hint here is ... "read until"
you can't know ahead how many numbers it will be, the pattern in this 
case is to use "while sum smaller then 100"
sum = 0
while sum < 100:
 sum = sum + input("more numbers please: ")


> that reads 100 numbers from the user and prints out the sum. "

here you know that you are going to read exactly 100 numbers
sum = 0
for i in range(100):
 sum = sum + input("please number #%i: " % (i+1))


the only unclear point here is range(100)
it generates a list with number [0,1,2 ... 99]
and iterates through it
one could write it like
for i in [0,1,2,3,4]:
 do_something_with(i)

but it gets tedious to write such a long list

> 
> but im not quite grasping those functions..
> 
> please bear im mind i am an extreme newbie at this...thanks in advance
> 

hth, Daniel
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Re: delete first line in a file

[Schüle Daniel]

Juergen Huber schrieb:
> Fredrik Lundh wrote:
>> Juergen Huber wrote:
>>
>>> ok...i thought as much, that i have to copy this file!
>>>
>>> how will i do that?!
>>> how will i fix this file => delete the first line?!
>>>
>>> with which commands could i do that?!
>> start here:
>>
>> http://docs.python.org/tut/node9.html#SECTION00920
>>
>> 
> 
> that documentation i have already read, but it wouldn`t help me for my
> problem!
> i know, how i can read the first line an print them on the screen!
> but...how can i say python, delete the first line?!
> thats my problem!
> in the entry of my posting i wrote, that i am a newbie and so please
> understand me, that i ask so questions?! :-)
> 
> thanks for your help!


simple!

f = file("old.file")
ignore = f.readline()
file("new.file", "w+").write(f.read())

hth, Daniel

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Re: string replace

[Schüle Daniel]

> A solution could be that "replace" accept a tuple/list of chars, like
> that was add into the new 2.5 for startswith.
> 
> I don't know, but can be this feature included into a future python 
> release?

I don't know, but I think it would be useful

as for now I use this

 >>> import re
 >>> chars = re.compile(r'[abc]')
 >>> text = "aAbBcCdD"
 >>> chars.sub("",text)
'ABCdD'
 >>>

> 
> Thanks,
> Michele

Regards, Daniel
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Re: How to control permission of file?

[Schüle Daniel]

Grant Edwards schrieb:
> When one open()s a file (that doesn't exist) for writing , how
> does one control that file's permissions (it's "mode" in Unix
> terms).

what do you mean by "contor file's mode"?

usually you try to open and if you are not allowed
you will get the exception

 >>> try:
... f = file("/etc/shadow")
... print f.read()
... except IOError, e:
... print e
...
[Errno 13] Permission denied: '/etc/shadow'
 >>>

if you want to know more about file attributes
use os.stat and constants from stat module

 >>> import os
 >>> os.stat("/etc/shadow")
(33184, 245390L, 771L, 1, 0, 15, 604L, 1151702662, 1149675585, 1149675585)
 >>>
 >>> import stat
 >>> stat.ST_SIZE
6
 >>> os.stat("/etc/shadow")[stat.ST_SIZE]
604L
 >>>

http://docs.python.org/lib/module-stat.html

hth, Daniel

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Re: How to control permission of file?

[Schüle Daniel]

> True, but I don't see what it has to do with my question.

my mistake, I misunderstood your question

as Sreeram said, os.open can be used


help(os.open)

Help on built-in function open:

open(...)
 open(filename, flag [, mode=0777]) -> fd

 Open a file (for low level IO).


 >>> import os
 >>> fd=os.open("secret", os.O_WRONLY|os.O_CREAT, 0400)
 >>> os.write(fd,"not for everybody")
17
 >>> os.close(fd)


ls -l secret
-r1 root root   17 2006-07-01 00:05 secret


Regards, Daniel
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Re: array of array of float

[Schüle Daniel]

[EMAIL PROTECTED] schrieb:
> i used C too much and haven't used Python for a while...
> 
> like in C, if we want an array of array of float, we use
> 
> float a[200][500];
> 
> now in Python, seems like we have to do something like
> 
> a = [ [ ] ] * 200
> 
> and then just use
> 
> a[1].append(12.34)   etc
> 
> but it turns out that all 200 elements points to the same list...
> and i have to use
> 
> a = [ ]
> for i in range (0, 200):
> a.append([ ])
> 
> is there a simpler way... i wonder...

a = [[] for in range(200)]
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Re: array of array of float

[Schüle Daniel]

Schüle Daniel schrieb:
> [EMAIL PROTECTED] schrieb:
>> i used C too much and haven't used Python for a while...
>>
>> like in C, if we want an array of array of float, we use
>>
>> float a[200][500];
>>
>> now in Python, seems like we have to do something like
>>
>> a = [ [ ] ] * 200
>>
>> and then just use
>>
>> a[1].append(12.34)   etc
>>
>> but it turns out that all 200 elements points to the same list...
>> and i have to use
>>
>> a = [ ]
>> for i in range (0, 200):
>> a.append([ ])
>>
>> is there a simpler way... i wonder...
> 
> a = [[] for in range(200)]

correction :)

a = [[] for i in range(200)]
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re question

[Schüle Daniel]

Hello,

consider the following code

 >>> re.search("[a-z](?i)[a-z]","AA")
<_sre.SRE_Match object at 0x40177e20>

this gives a match
if we provide an extra group for the first character it still works

 >>> re.search("([a-z])(?i)[a-z]","AA").group(1)
'A'
 >>>

it doesn't matter where (?i) is placed, right?
the re engine would glance at once on the entire pattern string
analize it (complain if pattern doesn't make sense, eg invalid)
and it would be the same as if the option was given expicitely
as re.IGNORECASE.

Is there a way to switch-off the option resp.
switch-on the option in the middle of the pattern?

Regards, Daniel
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how to convert a function into generator?

[Schüle Daniel]

Hello,

I came up with this algorithm to generate all permutations
it's not the best one, but it's easy enough

# lst = list with objects
def permute3(lst):
 tmp = []
 lenlst = len(lst)
 def permute(perm, level):
 if level == 1:
 tmp.append(perm)
 return
 for i in lst:
 if i not in perm:
 permute(perm + (i,), level - 1)
 for item in lst:
 permute((item,), lenlst)
 return tuple(tmp)

now I want to make a generator from it
the idea is to get each time a new permutation
I don't really understand how to handle the case
when my function has an inner function which has
a yield statement ..
I would say that the inner function becomes an generator
and stops&yields the value on each yield .. but in reality
I want to propogate these values to the caller of the outer function
I hope you got the idea of what I mean
the code is the sketch of the idea

def permute3gen(lst):
 lenlst = len(lst)
 def permute(perm, level):
 if level == 1:
 yield perm
 return # not sure return without a value is allowed, 
theoretically it could be replaces with if/else block
 for i in lst:
 if i not in perm:
 permute(perm + (i,), level - 1)
 for item in lst:
 yield permute((item,), lenlst) # makes generator from the outer 
function too


this is what I get

In [67]: reload permute
---> reload(permute)
Out[67]: 

In [68]: p =  permute.permute3gen(["a","b","c","d"])

In [69]: p
Out[69]: 

In [70]: x = p.next()

In [71]: y = p.next()

In [72]: x
Out[72]: 

In [73]: y
Out[73]: 

In [74]: x.next()
---
 Traceback (most recent call last)

/pool/PROG/python/permute/ in ()

:

I don't understand why the generator x raises StopIteration exception
I would expect that x.next() would call
permute(("a",), 4) and would stop at "abcd"

thanks in advance

regards, Daniel
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why is this different?

[Schüle Daniel]

Hello snakes :)

In [38]: f = [lambda:i for i in range(10)]
In [39]: ff = map(lambda i: lambda : i, range(10))
In [40]: f[0]()
Out[40]: 9
In [41]: f[1]()
Out[41]: 9
In [42]: ff[0]()
Out[42]: 0
In [43]: ff[1]()
Out[43]: 1

I don't understand why in the first case f[for all i in 0..9]==9
what is different from (more usefull)

In [44]: f = ["%i" % i for i in range(10)]
In [45]: f
Out[45]: ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']


doing it like this works again

In [54]: def d(x):
: return lambda:x
:

In [55]: f = [d(i) for i in range(10)]
In [56]: f[0]()
Out[56]: 0
In [57]: f[1]()
Out[57]: 1

in a C programmer sence I would say there seems to be no "sequence 
point" which would separate "now" from "next"

Regards, Daniel
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Re: why is this different?

[Schüle Daniel]

Gabriel Genellina schrieb:
Gabriel Genellina schrieb:
> On 7 dic, 22:53, Schüle Daniel <[EMAIL PROTECTED]> wrote:
> 
>> In [38]: f = [lambda:i for i in range(10)]
>> In [39]: ff = map(lambda i: lambda : i, range(10))
>> In [40]: f[0]()
>> Out[40]: 9
>> In [41]: f[1]()
>> Out[41]: 9
>> In [42]: ff[0]()
>> Out[42]: 0
>> In [43]: ff[1]()
>> Out[43]: 1
>>
>> I don't understand why in the first case f[for all i in 0..9]==9
> 
> In the first case, i is a free variable. That means that Python will
> get it from other place (the global namespace, likely [surely?])
> 
>>>> f=[lambda:i for i in range(10)]
>>>> f[0]()
> 9
>>>> i=123
>>>> f[0]()
> 123
>>>> print f[0].func_closure
> None
> 
> In the second case, the inner i is a free variable, but local to its
> enclosing scope (outer lambda). It's a closure:
>>>> ff = map(lambda i: lambda : i, range(10))
>>>> ff[4]()
> 4
>>>> ff[4].func_closure
> (,)
>>>> i=321
>>>> ff[4]()
> 4
> 
>> what is different from (more usefull)
>>
>> In [44]: f = ["%i" % i for i in range(10)]
>> In [45]: f
>> Out[45]: ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
> 
> This is a simple expression evaluated at each iteration
> 
>> doing it like this works again
>>
>> In [54]: def d(x):
>> : return lambda:x
>> :
> x inside lambda is a free variable, but since it's local to d, this
> becomes a closure:
> 
>>>> d(1)
>  at 0x00A35EF0>
>>>> d(1).func_closure
> (,)
> 
>> In [55]: f = [d(i) for i in range(10)]
>> In [56]: f[0]()
>> Out[56]: 0
>> In [57]: f[1]()
>> Out[57]: 1
> This is similar to the ff example above
> 
>> in a C programmer sence I would say there seems to be no "sequence
>> point" which would separate "now" from "next"
> 
> No, the problem is that C has no way to express a closure; this is a
> functional concept absolutely extraneous to the C language.
> 

> On 7 dic, 22:53, Schüle Daniel <[EMAIL PROTECTED]> wrote:
> 
>> In [38]: f = [lambda:i for i in range(10)]
>> In [39]: ff = map(lambda i: lambda : i, range(10))
>> In [40]: f[0]()
>> Out[40]: 9
>> In [41]: f[1]()
>> Out[41]: 9
>> In [42]: ff[0]()
>> Out[42]: 0
>> In [43]: ff[1]()
>> Out[43]: 1
>>
>> I don't understand why in the first case f[for all i in 0..9]==9
> 
> In the first case, i is a free variable. That means that Python will
> get it from other place (the global namespace, likely [surely?])
> 
>>>> f=[lambda:i for i in range(10)]
>>>> f[0]()
> 9
>>>> i=123
>>>> f[0]()
> 123
>>>> print f[0].func_closure
> None

intersting
I think I got it

[]

I have two more examples, but now I understand the difference

In [70]: x = [eval("lambda:i") for i in range(10)]
In [71]: y = [eval("lambda:%i" % i) for i in range(10)]

I think [71] is most obvious what the programmer intends

Thx
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backreference in regexp

[Schüle Daniel]

X-Enigmail-Version: 0.76.5.0
X-Enigmail-Supports: pgp-inline, pgp-mime
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit

Hello @all,

 >>> p = re.compile(r"(\d+) = \1 + 0")
 >>> p.search("123 = 123 + 0")

'search' returns None but I would expect it to
find 123 in group(1)

Am I using something that is not supported by Python
RegExp engine or what is the problem with my regexp?

Regards, Daniel

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Re: backreference in regexp

[Schüle Daniel]

thank you, I completely forgot that + is one of metacharacters

Regards, Daniel

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Re: Numeric and matlab

[Schüle Daniel]

Hello,

[...]
> 
> I'm sure there are more, but these jump out at me as I'm going.  It 
> seems as if the idx=find() stuff can be done with Numeric.nonzeros(), 
> but you can't index with that, like
> 
> a=Numeric.arange(1,11,1)
> idx=Numeric.nonzeros(a)

import Numeric as N
N.nonzero

without s :)

> a=a[idx]   % doesn't work

i don't know whether arange object overloads __getitem__
like

 >>> class X(object):
... def __getitem__(self,i):
... return self.lst[i]
... def __init__(self):
... self.lst = [7,5,3,1]
...
 >>> x=X()
 >>> x[0]
7
 >>> x[1]
5
 >>>

or consider

 >>> class List(list):
... def __getitem__(self,idx):
... if type(idx) is list:
... ret = []
... lst = list(self)
... return [lst[i] for i in range(len(lst)) if i in idx]
...
 >>> lst=List([1,2,3,4,5])
 >>> lst
[1, 2, 3, 4, 5]
 >>> lst[[0,2]]
[1, 3]
 >>>

if it would overload this would be possible, the normal
python list takes slices

range(0,100)[1:10:2]
s = slice(1,10,2)
range(0,100)[s]

here some ideas for what you tring to do

 >>> nums   # normal python list
[0, 1, 2, 1, 0, 0, 0, 3, 4, 0]
 >>> filter(lambda x: x!=0, nums)
[1, 2, 1, 3, 4]

 >>> [item for item in nums if item !=0 ]
[1, 2, 1, 3, 4]
 >>>

 >>> a=N.arange(0,11,.5)
 >>> filter(lambda x: x!=0, a)
[0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 
7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5]

 >>> [item for item in a if item !=0 ]
[0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 
7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5]

Regards, Daniel

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Re: read file problem

[Schüle Daniel]

if you want the numbers you can combine it into one-liner

nums = file(r"C:\folder\myFile.txt").read().split(";")

the numbers are in string representation in the list
you can no do

nums = [float(num) for num in nums]

Regards, Daniel

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Re: Size of list

[Schüle Daniel]

 >>> lst = [1,2,3]
 >>> len(lst)
3
 >>> lst.__len__()
3

in genereal all objects which implements __len__
can be passed to built-in function len
 >>> len


just to give one example how this can be used

 >>> class X(object):
... def __len__(self):
... print "this instance has __len__"
... return 100
...
 >>> x=X()
 >>> len(x)
this instance has __len__
100
 >>> x.__len__()
this instance has __len__
100

hth, Daniel

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Re: * 'struct-like' list *

[Schüle Daniel]

> I would like to have an array of "structs."  Each struct has
> 
> struct Person{
> string Name;
> int Age;
> int Birhtday;
> int SS;
> }


the easiest way would be

class Person:
pass

john = Person()
david = Person()

john.name = "John Brown"
john.age = 35
etc

think of john as namespace .. with attributes (we call them so) added on 
runtime

better approch would be to make real class with constructor

class Person(object):
def __init__(self, name, age):
self.name = name
self.age = age
def __str__(self):
return "person name = %s and age = %i" % (self.name, self.age)

john = Person("john brown", 35)
print john  # this calls __str__


> 
> I want to go through the file, filling up my list of structs.
> 
> My problems are:
> 
> 1.  How to search for the keywords "Name:", "Age:", etc. in the file...
> 2.  How to implement some organized "list of lists" for the data

this depend on the structure of the file
consider this format

New
Name: John
Age: 35
Id: 23242
New
Name: xxx
Age
Id: 43324
OtherInfo: foo
New

here you could read all as string and split it on "New"

here small example
 >>> txt = "fooXbarXfoobar"
 >>> txt.split("X")
['foo', 'bar', 'foobar']
 >>>

in more complicated case I would use regexp but
I doubt this is neccessary in your case

Regards, Daniel

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Re: how to copy a Python object

[Schüle Daniel]

[EMAIL PROTECTED] wrote:
> Already thanks for the reply,
> 
> but how to write your own copy operator? Won't you always be passing
> referrences to new_obj?

for example this would work

 >>> class X(object):
... def __init__(self,lst):
... self.lst = lst
... def copy(self):
... return X(self.lst[:])
... def __str__(self):
... return "lst has id %i" % id(self.lst)
...
 >>> x=X([1,2,3])
 >>> y=x.copy()
 >>> print x
lst has id 1078097132
 >>> print y
lst has id 1078097228


but I don't like that in this case self.lst must be passed
through __init__
I can think of another variant

 >>> class Y(object):
... def fill(self):
... self.lst = [randint(i*10,(i+1)*10) for i in xrange(5)]
... def __repr__(self):
... return "lst has id = %i" % id(self.lst)
... def copy(self):
... ret = Y()
... ret.lst = self.lst[:]
... return ret
...
 >>> from random import randint
 >>> y=Y()
 >>> y.fill()
 >>> y
lst has id = 1078097452
 >>> print y
lst has id = 1078097452
 >>> x=y.copy()
 >>> x
lst has id = 1078097004

... anyone?
are there better approaches?

Regards, Daniel

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Re: * 'struct-like' list *

[Schüle Daniel]

Ernesto wrote:
> Thanks for the approach.  I decided to use regular expressions.  I'm
> going by the code you posted (below).  I replaced the line re.findall
> line with my file handle read( ) like this:
> 
> print re.findall(pattern, myFileHandle.read())
> 
> This prints out only brackets [].  Is a 're.compile' perhaps necessary
> ?

if you see [] that means findall didn't find anything
that would match your pattern
if you re.compile your pattern beforehand that
would not make findall find the matched text
it's only there for the optimization

consider
lines = [line for line in file("foo.txt").readlines() if 
re.match(r"\d+",line)]

in this case it's better to pre-compile regexp one and use it
to match all lines

number = re.compile(r"\d+")
lines = [line for line in file("foo.txt").readlines() if number.match(line)]

fire interactive python and play with re and patterns
speaking from own experience ... the propability is
against you that you will make pattern right on first time

Regards, Daniel

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UnboundMethodType and MethodType

[Schüle Daniel]

Hello all,

 >>> class Q:
... def bar(self):
... pass
...
 >>> import types
 >>> types.UnboundMethodType is types.MethodType
True
 >>>
 >>> type(Q.bar)

 >>>
 >>> q = Q()
 >>> type(q.bar)

 >>>
 >>> type(q.bar) is types.UnboundMethodType
True
 >>> q.bar
>
 >>>

I think is not very consistent
notice q.bar is bounded although type(q.bar)
says it's types.UnboundedMethodType
what do you think?

Regard, Daniel

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Re: UnboundMethodType and MethodType

[Schüle Daniel]

[...]

>> It's the same function, whether it's bound or not. Thus, it should 
>> always have the same type. 
> 
> 
> No, it's not the same function. You got the same id because you didn't 
> bind B.bar and b.bar to anything so the id was reused.

thank you for the explanation
it's indeed tricky with reusing the id
are there some pages on the net to read more about it?

 >>> class Q:
... def __init__(self,val):
... self.val = val
... def bar(self):
... print self.val
...
 >>> x = Q.bar
 >>> y = Q("test").bar
 >>> x

 >>> y
>
 >>> y()
test
 >>> id(x)
1078081812
 >>> id(y)
1078082492
 >>>

the same id-value would enforce two objects to be
of the same type (trivial case)
the reverse is not necessarily true
in this case x.bar and y.bar are of the same type

UnboundMethodType is still not very suitable name for Q().bar
:-/

Regards, Daniel

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Re: is there a better way?

[Schüle Daniel]

[...]

> 
> What not
> 
> for x in list:
>   if x == O:
> break
>   storage.append(x)
> 

i think this may take too long
better aproach would be to test for zero from the end

Regards, Daniel

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Re: is there a better way?

[Schüle Daniel]

[...]

> I have been using something like this:
> _
> 
> while list[0] != O:
> storage.append(list[0])
> list.pop(0)
> if len(list) == 0:
> break
> _
> 
> But this seems ugly to me, and using "while" give me the heebies.  Is
> there a better approach?

 >>> lst = [1,2,3,4,5,0,0,0,0]
 >>> del lst[lst.index(0):]
 >>> lst
[1, 2, 3, 4, 5]
 >>>

Regards, Daniel

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Re: is there a better way?

[Schüle Daniel]

Lonnie Princehouse wrote:
> everybody is making this way more complicated than it needs to be.
> 
> storage = list[:list.index(O)]

the question is whether the old list is needed in the future or not
if not then it would be easer/mor efficient to use

del lst[lst.index(0):]

Regards, Daniel

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Re: is there a better way?

[Schüle Daniel]

I don't want to hijack the thread I was thinking
whether something like lst.remove(item = 0, all = True)
would be worth adding to Python?

it could have this signature

def remove(item, nItems = 1, all = False)
...
return how_many_deleted

lst.remove(item = 0, nItems = 1)
lst.remove(item = 0, nItems = 2)

lst.remove(item = 0, all = True)
in last case nItems is ignored

Regards, Daniel

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Re: arrays in python

[Schüle Daniel]

> I want to write a program in python using integer arrays.

you can :)


> I wish to calculate formulas using 200 digit integers.

no problem

> I could not find any documentation in python manual about declaring arrays.
>  
> I searched the internet

read here
http://diveintopython.org/native_data_types/lists.html

maybe list are what you are looking for

> and found an example that said I must declare
>  
> from Numeric import *

yes, one can use Numeric for this taks too

> and I downloaded a numerical python  extension,
>  
> but still  have not found a way to declare an array of given length.
>  
> The zeros function always gives me an error message.

 >>> import Numeric as N, random as rand
 >>> nums = [33 ** rand.randint(10,100) for i in range(200)]
 >>> len(nums)
200
 >>> nums[0]
1666465812864030391541732975677083441749008906546726522024522041932256405404932170047036994592860856233379702595619607481259213235163454890913L
 >>>
 >>> a = N.array(nums)
 >>> len(a)
200
 >>> a[0]
1666465812864030391541732975677083441749008906546726522024522041932256405404932170047036994592860856233379702595619607481259213235163454890913L
 >>>


by the way, you know you can use interactive Python iterpreter
and there is dir and help function

 >>> dir(a)
['__copy__', '__deepcopy__', 'astype', 'byteswapped', 'copy', 
'iscontiguous', 'itemsize', 'resize', 'savespace', 'spacesaver', 
'tolist', 'toscalar', 'tostring', 'typecode']
 >>> dir(nums)
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', 
'__delslice__', '__doc__', '__eq__', '__ge__', '__getattribute__', 
'__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', 
'__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', 
'__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', 
'__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', 
'__setslice__', '__str__', 'append', 'count', 'extend', 'index', 
'insert', 'pop', 'remove', 'reverse', 'sort']
 >>>

Regards, Daniel

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Re: Does python have an internal data structure with functions imported from a module?

[Schüle Daniel]

in case you are trying it in the python shell

 >>> def foo():return "test"
...
 >>> import __main__
 >>> __main__.__dict__["foo"]

 >>> __main__.__dict__["foo"]()
'test'
 >>>

otherwise build your own dict with string->function mapping

op = {
"plus" : lambda x,y:x+y,
"minus" : lambda x,y:x-y,
"power" : lambda x,y:x**y,
}

op["power"](2,8)

hth, Daniel

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Re: how to break a for loop?

[Schüle Daniel]

Gregory Petrosyan wrote:
> Hello!
> It's 1:56 o'clock in St.-Petersburg now, and I am still coding... maybe
> that's why I encountered stupid problem: I need to remove zeros from
> the begining of list, but I can't :-(. I use
> 
> for i,coef in enumerate(coefs):
> if coef == 0:
> del coefs[i]
> else:
> break
> 
> but it removes ALL zeros from list. What's up?

I don't know how enumerate is implemented, but I would
suspect that modifying the list object in the loop
through del is asking for trouble

try
for i,coef in enumerate(coefs[:]):
instead

> P.S. I feel SO stupid asking this quastion... ;-)

uda4i

hth, Daniel

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Re: Why I chose Python over Ruby

[Schüle Daniel]

Hi Alex

[...]

> The trick about distinguishing a name's exact nature based on whether
> the compiler sees an assignment to that name in some part of code is
> found in both languages, albeit in different ways. In Ruby, as you've
> pointed out, it's the heuristic used to disambiguate local variable
> access from zero-argument method calls, and the "part of code" is the
> function up to the point of access. In Python, it's used to disambiguate
> local from global or free variables, and the "part of code" is the body
> of the whole function (Ruby does not need to make this latter
> distinction because it strops global names with a leading sigil -- $a is
> always the global variable a, just like @a is always the instance
> attribute a, which we'd write self.a in Python). Another subtle case in
> Ruby is whether an assignment such as a=23 _within a block_ is meant to
> be local to the block or meant to rebind local name 'a' within the
> enclosing function; again, the heuristic is similar, depending only on
> whether the compiler had seen another assignment to a before it saw the
> block (Python forbids the rebinding of variables coming from an
> enclosing but non-global scope, to avoid facing this issue).

I am not sure what you mean here
can you elaborate on this please

 >>> def a():
... q = []
... def b(x):
... def c(y):
... def d(z):
... q.append(x)
... q.append(y)
... q.append(z)
... d(1)
... c(2)
... b(3)
... return q
...
 >>> a()
[3, 2, 1]

As far as I know this snippet would work only from version 2.2
maybe you are talking about older versions of Python

Regards, Daniel

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Re: Adding method at runtime - problem with self

[Schüle Daniel]

[EMAIL PROTECTED] wrote:
> First of all, please don't flame me immediately. I did browse archives
> and didn't see any solution to my problem.
> 
> Assume I want to add a method to an object at runtime. Yes, to an
> object, not a class - because changing a class would have global
> effects and I want to alter a particular object only. The following
> approach fails:
> 
> class kla:
> x = 1
> 
> def foo(self):
> print self.x
> 
> k = kla()
> k.foo = foo
> k.foo()
> 
> I know where the problem is. The method shouldn't have 'self'
> parameter. But how do I access object's attributes without it?
> 
> Best regards,
> 
> Marek
> 

k.foo(k)
would work

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pylab, matplotlib ... roots function question

[Schüle Daniel]

Hello NG,

given this call to roots funtion from pylab

In [342]: roots([0,2,2])
Out[342]: array([-1.])

as far as I understand it [a0,a1,a2] stands for a0+a1*x+a2*x^2
in the above case it yields 2x^2+2x = 2x(1+x)
and the roots are 0 and -1
I am wondering why roots function gives me only the -1

second try

In [343]: roots([1,0,0])
Out[343]: array([], dtype=float64)

ok, as it should be

In [344]: roots([0,0,1])
Out[344]: array([], dtype=float64)

here again, 0 is the root of x^2

Do I miss something important?


Regards, Daniel
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Re: pylab, matplotlib ... roots function question

[Schüle Daniel]

Hi,

[...]

> No, that's actually wrong. What version of numpy are you using? With a recent
> SVN checkout of numpy, I get the correct answer:
> 
> In [3]: roots([1,0,0])
> Out[3]: array([ 0.,  0.])

In [17]: import sys, numpy

In [18]: sys.version
Out[18]: '2.5 (r25:51908, Sep 23 2006, 01:23:14) \n[GCC 4.1.1]'

In [19]: numpy.version.version
Out[19]: '1.0rc1'


moon:/pool/PROG/python # uname -a
Linux moon 2.6.16.13-4-smp #1 SMP Wed May 3 04:53:23 UTC 2006 x86_64 
x86_64 x86_64 GNU/Linux

I think I will get and compile newer version of source

BTW, I also look for good (more or less complete and/or interessting)
tutoruals on signal processing with python
something like low/high-pass filtering/ploting of wave files etc
I would appreciate pointers very much.

I am learning this at the moment, when it all starts to make sense to
me, I will write such a tutorial on my own later

Regards, Daniel
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builtin set literal

[Schüle Daniel]

Hello,

lst = list((1,2,3))
lst = [1,2,3]

t = tupel((1,2,3))
t = (1,2,3)

s = set((1,2,3))
s = ...

it would be nice feature to have builtin literal for set type
maybe in P3 .. what about?
s = <1,2,3>

Regards, Daniel
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Re: builtin set literal

[Schüle Daniel]

faulkner schrieb:
> On Feb 14, 11:55 am, Schüle Daniel <[EMAIL PROTECTED]> wrote:
>> Hello,
>>
>> lst = list((1,2,3))
>> lst = [1,2,3]
>>
>> t = tupel((1,2,3))
>> t = (1,2,3)
>>
>> s = set((1,2,3))
>> s = ...
>>
>> it would be nice feature to have builtin literal for set type
>> maybe in P3 .. what about?
>> s = <1,2,3>
>>
>> Regards, Daniel
> 
> sets aren't quite that useful or common. just use a list.
> and '<' and '>' already have syntactic meanings.

well, I thought about this
the empty set <> has the meaning of != now
as far as I remember is <> depricated and will disappear
When they are gone in P3000, <> could be reused as empty set.

> and that would make python look more like C++, which nobody wants.

I dont think that actually many people fear this.
we have {} for dicts and I doubt anybody mistake them for C++ brakets.

In my previuos post I forgot to mention

d = dict()
d = {}

s = set()
s = <>

why not, on the first sight everybody will see ... here our
algorithmus deals with unique things/objects ... put in a set.

Regards, Daniel
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Re: builtin set literal

[Schüle Daniel]

Steven Bethard schrieb:
> Schüle Daniel wrote:
>> Hello,
>>
>> lst = list((1,2,3))
>> lst = [1,2,3]
>>
>> t = tupel((1,2,3))
>> t = (1,2,3)
>>
>> s = set((1,2,3))
>> s = ...
>>
>> it would be nice feature to have builtin literal for set type
>> maybe in P3 .. what about?
>> s = <1,2,3>
> 
> In Python 3.0, this looks like::
> 
> s = {1,2,3}

jepp, that looks not bad .. as in a mathe book.
the only disadvantage I see, that one may confuse it with a dict.

Regards, Daniel
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Re: builtin set literal

[Schüle Daniel]

[...]

>>> In Python 3.0, this looks like::
>>>
>>> s = {1,2,3}
>>
>> jepp, that looks not bad .. as in a mathe book.
>> the only disadvantage I see, that one may confuse it with a dict.
> 
> Perhaps with a very cursory inspection. But the lack of any ':' 
> characters is a pretty quick clue-in.

there is one a bigger disadvantage though
{} empty set clashes with empty dict {}
set() still must be used to generate the empty set
or a hack like
s = {None}.clear()

I think something like {-} as the substitution for empty set
will seem bit to perlish for most of us? :)

Regards, Daniel
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Re: builtin set literal

[Schüle Daniel]

> {:} for empty dict and {} for empty set don't look too much atrocious
> to me.

this looks consistent to me
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pylab, integral of sinc function

[Schüle Daniel]

Hello,

In [19]: def simple_integral(func,a,b,dx = 0.001):
: return sum(map(lambda x:dx*x, func(arange(a,b,dx
:

In [20]: simple_integral(sin, 0, 2*pi)
Out[20]: -7.5484213527594133e-08

ok, can be thought as zero

In [21]: simple_integral(sinc, -1000, 1000)
Out[21]: 0.99979735786416357

hmm, it should be something around pi
it is a way too far from it, even with a=-1,b=1

In [22]: def ppp(x):
: return sin(x)/x
:

In [23]: simple_integral(ppp, -1000, 1000)
Out[23]: 3.1404662440661117

nice

is my sinc function in pylab broken?
is there a better way to do numerical integration in pylab?

Regards, Daniel
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Re: pylab, integral of sinc function

[Schüle Daniel]

my fault

In [31]: simple_integral(lambda x:sinc(x/pi), -1000, 1000)
Out[31]: 3.14046624406611
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Re: pylab, integral of sinc function

[Schüle Daniel]

[...]

>> In [19]: def simple_integral(func,a,b,dx = 0.001):
>> : return sum(map(lambda x:dx*x, func(arange(a,b,dx
> 
> Do you mean
> 
>  def simple_integral(func,a,b,dx = 0.001):
> return dx * sum(map(func, arange(a,b,dx)))
> 

yes, this should be faster :)
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Re: Confused by Python and nested scoping (2.4.3)

[Schüle Daniel]

Sean Givan schrieb:
> Hi.  I'm new to Python

welcome

> ago.  I was doing some experiments with nested functions, and ran into 
> something strange.
> 
> This code:
> 
> def outer():
> val = 10
> def inner():
> print val
> inner()
> 
> outer()
> 
> ...prints out the value '10', which is what I was expecting.
> 
> But this code..
> 
> def outer():
> val = 10
> def inner():
> print val
> val = 20
> inner()
> print val
> 
> outer()
> 
> ...I expected to print '10', then '20', but instead got an error:
> 
>   print val
> UnboundLocalError: local variable 'val' referenced before assignment.
> 
> I'm thinking this is some bug where the interpreter is getting ahead of 
> itself, spotting the 'val = 20' line and warning me about something that 

just a little carefull thought
if something that basic should really be a bug
how many thousand people would discover it daily?

> doesn't need warning.  Or am I doing something wrong?

yes, you can't modify it
you can do it for global namespace or local
but not inbetween

val = 0
def outer():
val = 10
def inner():
global val
val = 30
inner()
print val
outer()
10  # outer val is not changed
print val   # global is modified
30

hth, Daniel

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can someone explain why ..

[Schüle Daniel]

I don't understand what is the difference between commented lines
1 and 2

with 1 uncommented and 2 commented it works as expected
with 1 commented and 2 uncommented the picture doesn't appear

here is my code

#!/usr/bin/env python

from Tkinter import *
from Tkconstants import *

root = None

class Main:
 def __init__(self):
 global root
 root = Tk(className = "Zeitrechner")
 root.config(borderwidth = 5, relief = GROOVE)
 root.geometry("0x0+100+50")

 #self.im = image = PhotoImage(file = "./flower1.gif")  #1
 image = PhotoImage(file = "./flower1.gif") #2
 frame1 = Frame(master = root, borderwidth = 3, relief = SUNKEN)
 imageLabel = Label(master = frame1, image = image)

 root.minsize(width = image.width(), height = image.height())
 root.maxsize(width = 2*image.width(), height = image.height())

 imageLabel.pack()
 frame1.pack(side = LEFT)

 def mainloop(self):
 root.mainloop()

main = Main()
main.mainloop()
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Re: can someone explain why ..

[Schüle Daniel]

Farshid Lashkari schrieb:
> Schüle Daniel wrote:
>> I don't understand what is the difference between commented lines
>> 1 and 2
>>
>> with 1 uncommented and 2 commented it works as expected
>> with 1 commented and 2 uncommented the picture doesn't appear
> 
> 
> I'm not familiar with Tkinter, but it seems as thought with 2, the 
> "image" variable is garbage collected after the constructor of Main is 
> called. With 1, you save a reference to the image, so it does not get 
> garbage collected.

thx for quick reply :)

image is local variable of imageLabel
I would expect that in case imageLabel lives, it should
hold alife objects bound to its local variables

I am just curious *why* reference to image is not hold by imageLabel
which on his part is hold by frame1 .. which is hold by global root

Regards, Daniel

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Re: can someone explain why ..

[Schüle Daniel]

[..]

> These are the only lines of code that reference "imageLabel":
> 
> imageLabel = Label(master = frame1, image = image)
> imageLabel.pack()
> 
> 
> Unless the constructor of Label adds a reference of itself to frame1, 
> imageLabel will also become garbage collected at the end of the 
> constructor. Are you sure this is the case?

yes, now i see it
even can frame1 be dead after __init__
it binds itself too root with

frame1 = Frame(master = root)
frame1.pack(side = LEFT)

frame1.pack may append frame1 to root's list of all
widgets, we cannot see it, but it also may not do it

Thx
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can this be done without eval/exec?

[Schüle Daniel]

Hello group,

 >>> lst=[]
 >>> for i in range(10):
... lst.append(eval("lambda:%i" % i))
...
 >>> lst[0]()
0
 >>> lst[1]()
1
 >>> lst[9]()
9
 >>>

 >>> lst=[]
 >>> for i in range(10):
... exec "tmp = lambda:%i" % i  # assignment is not expression
... lst.append(tmp)
...
 >>> lst[0]()
0
 >>> lst[1]()
1
 >>> lst[9]()
9
 >>>

and now the obvious one (as I thought at first)

 >>> lst=[]
 >>> for i in range(10):
... lst.append(lambda:i)
...
 >>> lst[0]()
9
 >>> i
9
 >>>

I think I understand where the problem comes from
lambda:i seems not to be fully evalutated
it just binds object with name i and not the value of i
thus lst[0]() is not 0

are there other solutions to this problem
without use of eval or exec?

Regards, Daniel
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Re: can this be done without eval/exec?

[Schüle Daniel]

>> are there other solutions to this problem
>> without use of eval or exec?
>>
> 
> Using a factory function & closures instead of lambda:

 >>> def a(x):
... def b():
... return x
... return b
...
 >>> lst=[]
 >>> for i in range(10):
... lst.append(a(i))
...
 >>> lst[0]()
0
 >>> lst[1]()
1
 >>> lst[9]()
9
 >>>

yes this works
I was playing a little more with this idea
and got into the next trouble :)

 >>> cnt=0
 >>> def a():
... def b():
... return cnt
... global cnt
... cnt += 1
... return b
...
 >>> lst=[]
 >>> for i in range(10):
... lst.append(a())
...
 >>> lst[0]()
10
 >>> lst[1]()
10
 >>>

I figured out what was wrong, here is corrected version

 >>> cnt = 0
 >>> def a():
... global cnt
... tmp = cnt
... def b():
... return tmp
... cnt += 1
... return b
...
 >>> lst=[]
 >>> for i in range(10):
... lst.append(a())
...
 >>> lst[0]()
0
 >>> lst[1]()
1
 >>>

Regards, Daniel
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Re: can this be done without eval/exec?

[Schüle Daniel]

Kent Johnson schrieb:
> Schüle Daniel wrote:
>> and now the obvious one (as I thought at first)
>>
>>  >>> lst=[]
>>  >>> for i in range(10):
>> ... lst.append(lambda:i)
>> ...
>>  >>> lst[0]()
>> 9
>>  >>> i
>> 9
>>  >>>
>>
>> I think I understand where the problem comes from
>> lambda:i seems not to be fully evalutated
>> it just binds object with name i and not the value of i
>> thus lst[0]() is not 0
> 
> The problem is that variables in closures are not bound until the 
> variable goes out of scope. So each lambda is bound to the final value 
> of i.
>>
>> are there other solutions to this problem
>> without use of eval or exec?
> 
> The workaround is to use a default argument to bind the current value of i:
> In [1]: lst = []
> 
> In [2]: for i in range(10):
>...: lst.append(lambda i=i: i)
>...:
>...:
> 
> In [3]: lst[0]()
> Out[3]: 0
> 
> In [4]: lst[5]()
> Out[4]: 5
> 
> A list comp makes this IMO cleaner:
> In [5]: lst = [ lambda i=i: i for i in range(10) ]
> 
> In [6]: lst[0]()
> Out[6]: 0
> 
> In [7]: lst[5]()
> Out[7]: 5
> 
> Kent

many thanks for the explaination,
it look much simpler than my solutions too

Daniel
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deriving from complex

[Schüle Daniel]

Hello

I am trying to customize the handling of complex numbers
what I am missing is a builtin possibility to create
complex numbers in polar coordinates

so first I wrote a standalone function

 >>> def polar(r,arg):
... re, im = r*cos(arg), r*sin(arg)
... return re + im*1j

then I tried to extend this to a class

 >>> from math import *

 >>> class Complex(complex):
... def __init__(self,x,y,polar=False):
... if not polar:
... self.re, self.im = x,y
... else:
... self.re, self.im = x*cos(y), x*sin(y)
...
 >>>
 >>> c=Complex(1,1)
 >>> c
(1+1j)
 >>> p=Complex(10,45.0/360*2*pi,True)
Traceback (most recent call last):
   File "", line 1, in ?
TypeError: complex() takes at most 2 arguments (3 given)
 >>>

and got stuck with this error
it seems that last argument is rejected
because complex wants to have 2 arguments
but this works well ..

 >>> class X(object):
... def __init__(self,a):
... self.a = a
...
 >>> class Y(X):
... def __init__(self,a,b):
... self.a = a
... self.b = b
...
 >>> y=Y(1,2)

what's causing the above exception?

one more question

 >>> class Complex(complex):
... def __init__(self,x,y):
... self.real = x
... self.imag = y
...
 >>> c=Complex(1,1)
Traceback (most recent call last):
   File "", line 1, in ?
   File "", line 3, in __init__
TypeError: readonly attribute
 >>>

how can I work around this problem?

Regards, Daniel

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Re: deriving from complex

[Schüle Daniel]

what do you think of this design?

 >>> def polar(x,y=None):
... if type(x) in (list,tuple) and len(x) == 2 and y is None:
... return complex(x[0]*cos(x[1]), x[0]*sin(x[1]))
... if type(x) is complex and y is None:
... return (abs(x), atan2(x.imag,x.real))
... if type(x) in (float, int, long) and type(y) in (float, int, long):
... return complex(x*cos(y), x*sin(y))
...
 >>> polar(2**0.5, 45.0/360*2*pi)
(1.0002+1j)
 >>> polar((2**0.5, 45.0/360*2*pi))
(1.0002+1j)
 >>> polar([2**0.5, 45.0/360*2*pi])
(1.0002+1j)
 >>> polar(1+1j)
(1.4142135623730951, 0.78539816339744828)
 >>>

btw I like how Ruby handles the creation of complex numbers

c = Complex(1,1)
p = Complex.polar(1,45.0/360*2*PI)

Regards, Daniel

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Re: deriving from complex

[Schüle Daniel]

thank you
I will have to take a closer look on __new__

Regards, Daniel

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[exec cmd for cmd in cmds]

[Schüle Daniel]

Hello all,

 >>> p = "z%i = complex(1-1e-%i, 1-1e-%i)"
 >>> lst = [p % (i,i,i) for i in range(10, 30)]
 >>> for item in lst:
... exec item
...
 >>>
 >>> p = "z%i = complex(1-1e-%i, 1-1e-%i)"
 >>> lst = [p % (i,i,i) for i in range(10, 30)]
 >>> [exec item for item in lst]
   File "", line 1
 [exec item for item in lst]
 ^
SyntaxError: invalid syntax
 >>>

is this prohibited for some reasons or is this just happens to be
disallowed?


this is one more cool way
 >>> p = "z%i = complex(1-1e-%i, 1-1e-%i);"
 >>> c = reduce(lambda x,y: x+y, [p % (i,i,i) for i in range(20,30)])
 >>> exec c

and one more :)
 >>> p = "z%i = complex(1-1e-%i, 1-1e-%i);"
 >>> c = "".join([ p % (i,i,i) for i in range(20,30) ])
 >>> exec c

Regards, Daniel

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Re: [exec cmd for cmd in cmds]

[Schüle Daniel]

[...]

> If you think so :) Ususally people go for dictionaries in such cases.

you are right, I didn't think about dictionaries

 >>> p = "complex(1-1e-%i, 1-1e-%i)"
 >>> d={}
 >>> [d.update({i:eval(p % (i,i))}) for i in range(20,30)]
[None, None, None, None, None, None, None, None, None, None]

so now the work is complete :)

Regards

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Re: Inter-module globals

[Schüle Daniel]

Anton81 wrote:
> Hi,
> 
> I want to use globals that are immediately visible in all modules. My
> attempts to use "global" haven't worked. Suggestions?
> 
> Anton

I think a dictionary would work here
as well as list but not strings and int's

# module1
settings = {
"release" : "1.0",
"blabla"  : None,
}

# module2
import module1 as settings
print settings.settings["release"]
settings.settings["blabla"] = True


# module3
import module1 as settings
settings.settings["blabla"] = False

Regards

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Re: A better RE?

[Schüle Daniel]

Magnus Lycka wrote:
> I want an re that matches strings like "21MAR06 31APR06 1236",
> where the last part is day numbers (1-7), i.e it can contain
> the numbers 1-7, in order, only one of each, and at least one
> digit. I want it as three groups. I was thinking of
> 
> r"(\d\d[A-Z]\d\d) (\d\d[A-Z]\d\d) (1?2?3?4?5?6?7?)"
> 
> but that will match even if the third group is empty,
> right? Does anyone have good and not overly complex RE for
> this?
> 
> P.S. I know the "now you have two problems reply..."

 >>> txt = "21MAR06 31APR06 1236"

 >>> m = '(?:JAN|FEB|MAR|APR|MAI|JUN|JUL|AUG|SEP|OCT|NOV|DEZ)'
# non capturing group (:?)

 >>> p = re.compile(r"(\d\d%s\d\d) (\d\d%s\d\d) 
(?=[1234567])(1?2?3?4?5?6?7?)" % (m,m))

 >>> p.match(txt).group(1)
'21MAR06'

 >>> p.match(txt).group(2)
'31APR06'

 >>> p.match(txt).group(3)
1236

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Re: output formatting for classes

[Schüle Daniel]

Russ wrote:
> I'd like to get output formatting for my own classes that mimics the
> built-in output formatting. For example,
> 
> 
x = 4.54
print "%4.2f" % x
> 
> 4.54
> 
> In other words, if I substitute a class instance for "x" above, I'd
> like to make the format string apply to an element or elements of the
> instance. Can I somehow overload the "%" operator for that? Thanks.
> 
> On an unrelated matter, I think the complex class in Python is too
> complex, so I plan to clean it up and implement it right. (just
> kidding, folks!)

yeah, i miss some things in complex implementation
for example c=complex()
c.abs = 2**0.5
c.angle = pi/2

should result in 1+1j :)

or c=complex(1,1)
print c.abs # should print 2**0.5
print c.angle # should print pi%2

i think one can implement it with properties

but to your question ...

 >>> class X(object):
... def __float__(self):
... return 1.0
... def __long__(self):
... return 10l
... def __int__(self):
... return 20
... def __repr__(self):
... return "i am"
... def __str__(self):
... return "I AM"
... def __complex__(self):
... return 1+1j
...
 >>> x=X()
 >>> int(x)
20
 >>> long(x)
10L
 >>> float(x)
1.0
 >>> str(x)
'I AM'
 >>> repr(x)
'i am'
 >>> print "%s -- %r" % (x,x)
I AM -- i am
 >>> complex(x)
(1+1j)
 >>>

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Re: Mutable complex numbers [was Re: output formatting for classes]

[Schüle Daniel]

Steven D'Aprano wrote:
> On Fri, 10 Mar 2006 02:19:10 +0100, Schüle Daniel wrote:
> 
> 
>>yeah, i miss some things in complex implementation
>>for example c=complex()
>>c.abs = 2**0.5
>>c.angle = pi/2
>>
>>should result in 1+1j :)
> 
> 
> Smiley noted, but consider:
> 
> c = complex()
> => what is the value of c here?

default value is 0, for complex number that means
real = 0, imag = 0
is the same as
c.abs=0, c.angle=0

ok mathematically c.angle can be of arbitrary value
but defaulting it to zero is very handy
c = complex()
c.abs = 10
yields 10+0j

c=complex()
c.real = 2
c.imag = 2
c.abs = 50**0.5 # angle remains, length changed
yields 5+5j
c.angle = 0
yields 50**0.5 + 0j

> c.abs = 2**0.5
> => what is c's value now?

c.abs = 2**0.5
c.angle = 0

> 
> c.angle = pi/2
> => now c has the value 1+1j
>  
> Objects with indeterminate values are rarely a good idea.

IMHO it's perfectly consistent with
 >>> int()
0
 >>> long()
0L
 >>> float()
0.0
 >>>
complex()
 >>> complex()
0j
 >>>

but extending complex with default angle=0



> A better way would be for complex numbers to take a constructor that can
> take arguments in either Cartesian or polar form. So, hypothetically, the
> following would all be equivalent:
> 
> 1+1j
> complex(1,1)
> complex(real=1, img=1)
> complex(len=2**0.5, theta=pi/2)

ack
but after the creation of complex number one will have to
do all the transformations in another coord. system manually

> Another alternative would be a function to construct polar form complex
> numbers. It could be a plain function or a static method:
> 
> cmath.polar(2**0.5, pi/2) => 1+1j
> complex.polar(2**0.5, pi/2) => 1+1j

maybe adding

c=complex.from_polar((length,angle))
d=complex.to_polar(c)
d == (length, angle)
True

would be sufficient, but I would prefer the other version

Regards

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__slots__ in derived class

[Schüle Daniel]

Hello,

consider this code

 >>> class A(object):
... def __init__(self):
... self.a = 1
... self.b = 2
...
 >>> class B(A):
... __slots__ = ["x","y"]
...
 >>> b=B()
 >>> b.a
1
 >>> b.b
2
 >>> b.x = 100
 >>> b.y = 100
 >>> b.z = 100

no exception here
does __slots__ nothing when used in derived classes?


 >>>
 >>>
 >>> class Z(object):
... __slots__ = ["x","y"]
...
 >>> z=Z()
 >>> z.x = 100
 >>> z.y = 100
 >>> z.z = 100
Traceback (most recent call last):
   File "", line 1, in ?
AttributeError: 'Z' object has no attribute 'z'
 >>>

here it works like expected

Regards, Daniel

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Re: "pow" (power) function

[Schüle Daniel]

Russ wrote:
> I have a couple of questions for the number crunchers out there:
> 
> Does "pow(x,2)" simply square x, or does it first compute logarithms
> (as would be necessary if the exponent were not an integer)?
> 
> Does "x**0.5" use the same algorithm as "sqrt(x)", or does it use some
> other (perhaps less efficient) algorithm based on logarithms?

you can try and timeit

 >>> 111**111
10736201288847422580121456504669550195985072399422480480477591117562507619578334702249122617009363462146610374309298696786330067310159463303558666910091026017785587295539622142057315437069730229375357546494103400699864397711L
 >>> timeit.Timer("pow(111,111)").timeit()
40.888447046279907
 >>> timeit.Timer("111**111").timeit()
39.732122898101807
 >>> timeit.Timer("111**0.5").timeit()
2.0990891456604004
 >>> timeit.Timer("pow(111,0.5)").timeit()
4.1776390075683594
 >>> timeit.Timer("111**0.3").timeit()
2.3824679851531982
 >>> timeit.Timer("pow(111,0.3)").timeit()
4.2945041656494141

interesting result
seems that ** computates faster

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int <-> str asymmetric

[Schüle Daniel]

Hello

what I sometimes miss in Python is the possibility to
switch tha base of a number
for example this is how it's done in Ruby

irb(main):099:0* a = 10.to_s(2)
=> "1010"
irb(main):100:0> a.to_i(2)
=> 10
irb(main):101:0>
irb(main):102:0* a = 10.to_s(3)
=> "101"
irb(main):103:0> a.to_i(3)
=> 10

the Python int-Function behaves similar
 >>> int("1010",2)
10
 >>>

however we lack the reverse functionality
the logical

 >>> str(10,2)
Traceback (most recent call last):
   File "", line 1, in ?
TypeError: str() takes at most 1 argument (2 given)
 >>>

fails

it would not break anything if str interface would be changed
what do you think?
Is this already proposed or maybe implemented in 2.5?

Regards, Daniel

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Re: what's going on here?

[Schüle Daniel]

[...]

> So finally here's my question: If you are using data.append(), doesn't 
> that just put all the numbers into one long list? 

no, append appends
extend does what you think

How are the tuples
> still being created in this case so that the list comprehensions still 
> work? It seems like there is no longer any 'row' to refer to in data.

why not to fire interpreter to see what happens

 >>> line1 = "1 2 3 4"
 >>> line2 = "5 6 7 8"
 >>> lst = []
 >>> lst.append(map(float, line1.split()))
 >>> lst
[[1.0, 2.0, 3.0, 4.0]]
 >>> lst.append(map(float, line2.split()))
 >>> lst
[[1.0, 2.0, 3.0, 4.0], [5.0, 6.0, 7.0, 8.0]]
 >>>


hth, Daniel

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Re: My Generator Paradox!

[Schüle Daniel]

it's easy to explain

class X:
pass

x=X()
y=X()

x and y are different instances
one can put in x
x.item = 1
y doesn't even have an attribute item for example

similar with generators
they are *different* objects of same kind generator

 >>> def fib():
... a,b = 1,1
... while True:
... a,b = b,a+b
... yield a,b
...
 >>> f1 = fib()
 >>> f2 = fib()
 >>> f1

 >>> f2
# different addresses
 >>> f1 is f2
False
 >>> f1.next()
(1, 2)
 >>> f1.next()
(2, 3)
 >>> f1.next()
(3, 5)
 >>>
 >>>
 >>> f2.next()
(1, 2)
 >>>

it's only natural that each objects starts it's own fibonaci serie

hth, Daniel

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Re: Help - strange behaviour from python list

[Schüle Daniel]

Sean Hammond schrieb:
> 
> I've managed to create a scenario in which editing an object in a list 
> of objects seems to edit every object in the list, rather than just the 
> one. I'm totally stumped and wondered if anyone would be kind enough to 
> read my explanation and see if they have any suggestions. I have 
> probably stumbled into some typical newbie problem, but anyway:
> 

just a hint

 >>> def foo(val,lst=[]):
... lst.append(val)
... print lst
...
 >>>
 >>>
 >>> foo(1)
[1]
 >>> foo(2)
[1, 2]
 >>> foo(3)
[1, 2, 3]
 >>> foo(4,[0])
[0, 4]
 >>>

here list lst is created and bound once


compare with this one (which is what you really want)

 >>> def bar(val, lst=None):
... if lst is None:
... lst = []
... lst.append(val)
... print lst
...
 >>> bar(1)
[1]
 >>> bar(2)
[2]
 >>> bar(3, [0])
[0, 3]
 >>>

hth, Daniel
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