Re: How to print something only if it exists?
On 6/09/12 19:59:05, tinn...@isbd.co.uk wrote: > I want to print a series of list elements some of which may not exist, > e.g. I have a line:- > > print day, fld[1], balance, fld[2] > > fld[2] doesn't always exist (fld is the result of a split) so the > print fails when it isn't set. How about: print day, fld[1], balance, fld[2] if len(fld) > 2 else '' If you really want to avoid the keyword 'if', then you'd have to do something like: print day, fld[1], balance, (fld[2:3] or [''])[0] That may be shorter, but it isn't very readable. Hope this helps, -- HansM -- http://mail.python.org/mailman/listinfo/python-list
Re: Python newbie here! No module named settings
On Thursday, June 2, 2011 8:59:48 PM UTC+5:30, Neeraj Agarwal wrote: > Hello all, > > I'm a newbie to Python and its my 2nd day exploring it. > > I was trying to use Python wrapper for Google Charts API and was > tweaking the examples. > https://github.com/gak/pygooglechart/raw/master/examples/pie.py > > This is the script which I was trying. > > And the python interpreter gives the following error: > import settings > ImportError: No module named settings > > I installed Django as well before this (if its causing the problem, > dunno) > > Please help me. > > Thanks, > Neeraj hi neeraj, I am also experiencing the same problem and in my pygooglechart file i am not having both settings.py and __init__.py file so can you send me the link from where you downloaded api Best Regards, ganesh -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing dll
On Fri, Sep 7, 2012 at 1:44 AM, Helpful person wrote: > FYI > > My Python version is 2.5.4 You may wish to upgrade, that's quite an old version. Unless something's binding you to version 2.x, I would strongly recommend migrating to 3.2 or 3.3. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Division help in python
Hi All, I am brand new to python. checking over basic stuff. I came across the problem while doing so. If any body aware of the problem, kindly respond me. >>> 5/10 0 >>> - 5/10 -1 The second case also should yield a 'zero' but it is giving a -1 some other examples for your review. >>> -10/5 -2 >>> -5/-5 1 >>> 1/2 0 >>> -1/2 -1 >>> -1 /4 -1 I would be thankful to you if i got through this. Ramya -- http://mail.python.org/mailman/listinfo/python-list
Re: Division help in python
On Fri, Sep 7, 2012 at 10:53 PM, Ramyasri Dodla wrote: > I am brand new to python. checking over basic stuff. I came across the > problem while doing so. If any body aware of the problem, kindly respond me. > 5/10 > 0 - 5/10 > -1 > > The second case also should yield a 'zero' but it is giving a -1 You're clearly using Python 2, because in Python 3, the / operator will return a float instead (so these would return 0.5 and -0.5 respectively). But it's helpful to mention what Python version you're using when you ask for help :) The reason for this is that / (or in Python 3, //) rounds toward negative infinity, not toward zero. This allows the modulo operator (%) to return a positive number, while still maintaining the normal expectation that: (x//y)*y + (x%y) == x for any two integers x and y. Hope that helps! ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to print something only if it exists?
In article <9s4nh9-8dr@chris.zbmc.eu>, tinn...@isbd.co.uk wrote: > I want to print a series of list elements some of which may not exist, > e.g. I have a line:- > > print day, fld[1], balance, fld[2] > > fld[2] doesn't always exist (fld is the result of a split) so the > print fails when it isn't set. > > I know I could simply use an if but ultimately there may be more > elements of fld in the print and the print may well become more > complex (most like will be formatted for example). Thus it would be > good if there was some way to say "print this if it exists". One possible way is a trick I've used in the past. fld = split(...) + ['']*10 this guarantees that fld has at least 10 elements. If you want to guarantee that fld has *exactly* 10 elements, just take [0:10] of that. -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitshifts and "And" vs Floor-division and Modular
On 07/09/2012 02:08, Cameron Simpson wrote: On 07Sep2012 01:30, Mark Lawrence wrote: | On 07/09/2012 01:01, jimbo1qaz wrote: | > Is it faster to use bitshifts or floor division? And which is better, & or %? | > All divisors and mods are power of 2, so are binary operations faster? And are they considered bad style? | | Why don't you use the timeit module and find out for yourself? Because timeit doesn't output style advice? Because timeit won't offer even a short single parapgraph description of how python ints (even just in CPython) are implemented and how that may affect performance in general? To the OP: personally, I would suggest using % when I am thinking of division and a bit shift when I am thinking of a bitshift, and only reach for timeit when performance becomes an issue. Code for the algoritm, and only optimise later. Of course only a well run benchmark will measure the real world, but it possible to address his other questions in a helpful fashion and address the benchmark question in a less offputting tone. If you can't be bothered, please don't. (Especially since these irritating posts from you are usually in response to a post you feel could have used more effort from the OP.) Nobody answers all performance considerations or design choices with an exhaustive timeit benchmark, and it is silly to suggest so. It is helpful for people to have a mental model of the python internals so they can make often-sensible choices from the start. So try being helpful instead of slapping people down when they haven't reached your private bar. Cheers, I'm sorry but I refuse point blank to spoon feed, fit bibs and change nappies. I wouldn't do that on the tutor mailing list and I certainly wouldn't do it here. If any OP is too bone idle to do some research and then pose a sensible question relating to what they want to achieve, what they've done to achieve it and what issues they've got then I intend responding in the same way. Clearly your approach is different so we'll have to agree to disagree. -- Cheers. Mark Lawrence. -- http://mail.python.org/mailman/listinfo/python-list
Defining features in a list
Good Morning,
I have been recently trying to define all of the features in a list but have
been running into errors. I would like to define the features similar to the
following print statement. Any advice would be appreciated. I'm trying to
transition my output from a text file to excel and if I can loop through my
lists and define them that transition will be cleaner.
Many Thanks,
-Matt
#Author: MGW
#2012
import os, datetime, sys, arcpy, xlrd
from arcpy import env
submission = "Rev.mdb"
env.workspace = "C:/temp/"+submission+"/Water"
#Get Submission totals
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
print fc+"="+str(arcpy.GetCount_management(fc).getOutput(0))
print "Complete"
raw_input("Press ENTER to close this window")
Output Generated
WATER_Net_Junctions=312
WS_Hyd=484
WS_Mains=2752
WS_Node=4722
WS_Vlvs=1078
WS_WatLats=3661
WS_WatMtrs=3662
WTRPLANTS_points=0
WTRPUMPSTA_points=0
WTRTANKS=0
WTR_ARV=10
WTR_MISC=0
Complete
Press ENTER to close this window
#Get Submission totals
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
fc=str(arcpy.GetCount_management(fc).getOutput(0))
#TEST
print WS_Hyd
print "Complete"
raw_input("Press ENTER to close this window")
Output Generated
Traceback (most recent call last):
File "C:\Documents and Settings\mattheww\Desktop\Copy of QAQCexce_2.py", line
14, in
print WS_Hyd
NameError: name 'WS_Hyd' is not defined
--
http://mail.python.org/mailman/listinfo/python-list
Re: Bitshifts and "And" vs Floor-division and Modular
On 2012-09-07, Steven D'Aprano wrote: > My *guess* is that you mean *bitwise* operators, compared to numeric > operators like * and // (integer division). The runtime cost is mostly > dominated by the object-oriented overhead -- Python is not C or assembly, > and the integers are rich objects, not low-level bitfields, so the > difference between division and bitshifting is much less than you might > expect from assembly language. I don't suppose there's much of a chance that the OP is running Python on a CPU that doesn't have an integer divide instruction? If that _were_ the case, the difference would be more noticable, but would still probably not worth worrying about unless a truely huge number of operations were being done in a very tight loop with no intervening I/O operations. -- Grant Edwards grant.b.edwardsYow! I have accepted at Provolone into my life! gmail.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Function for examine content of directory
kl. 16:56:29 UTC+2 torsdag 6. september 2012 skrev Tigerstyle følgende:
> Hi guys,
>
>
>
> I'm trying to write a module containing a function to examine the contents of
> the current working directory and print out a count of how many files have
> each extension (".txt", ".doc", etc.)
>
>
>
> This is the code so far:
>
> --
>
> import os
>
>
>
> path = "v:\\workspace\\Python2_Homework03\\src\\"
>
> dirs = os.listdir( path )
>
> filenames = {"this.txt", "that.txt",
> "the_other.txt","this.doc","that.doc","this.pdf","first.txt","that.pdf"}
>
> extensions = []
>
> for filename in filenames:
>
> f = open(filename, "w")
>
> f.write("Some text\n")
>
> f.close()
>
> name , ext = os.path.splitext(f.name)
>
> extensions.append(ext)
>
>
>
> # This would print all the files and directories
>
> for file in dirs:
>
> print(file)
>
>
>
> for ext in extensions:
>
> print("Count for %s: " %ext, extensions.count(ext))
>
>
>
> --
>
>
>
> When I'm trying to get the module to print how many files each extension has,
> it prints the count of each ext multiple times for each extension type. Like
> this:
>
>
>
> this.pdf
>
> the_other.txt
>
> this.doc
>
> that.txt
>
> this.txt
>
> that.pdf
>
> first.txt
>
> that.doc
>
> Count for .pdf: 2
>
> Count for .txt: 4
>
> Count for .doc: 2
>
> Count for .txt: 4
>
> Count for .txt: 4
>
> Count for .pdf: 2
>
> Count for .txt: 4
>
> Count for .doc: 2
>
>
>
> Any help is appreciated.
>
>
>
> T
--
http://mail.python.org/mailman/listinfo/python-list
Re: Function for examine content of directory
Ok I'm now totally stuck.
This is the code:
---
import os
from collections import Counter
path = ":c\\mypath\dir"
dirs = os.listdir( path )
filenames = {"this.txt", "that.txt",
"the_other.txt","this.doc","that.doc","this.pdf","first.txt","that.pdf"}
extensions = []
for filename in filenames:
f = open(filename, "w")
f.write("Some text\n")
f.close()
name , ext = os.path.splitext(f.name)
extensions.append(ext)
# This would print all the files and directories
for file in dirs:
print(file)
for ext, count in Counter(extensions).items():
print("Count for %s: " % ext, count)
---
I need to make this module into a function and write a separate module to
verify by testing that the function gives correct results.
Help and pointers are much appreciated.
T
--
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Re: Defining features in a list
On 09/07/2012 09:42 AM, M Whitman wrote:
> Good Morning,
>
> I have been recently trying to define all of the features in a list but have
> been running into errors.
How proficient are you in Python? Could you possibly use terms which
make sense to someone who doesn't know this arcGIS program? I'm just
making a wild guess that that's what you're importing with the arcpy
import. When I do an internet search on arcpy, I see lots of tutorials,
training, etc. I didn't find a mailing list, but there probably is one.
The term that needs translating is "feature.'
> I would like to define the features similar to the following print
> statement. Any advice would be appreciated. I'm trying to transition my
> output from a text file to excel and if I can loop through my lists and
> define them that transition will be cleaner.
>
> Many Thanks,
>
> -Matt
>
> #Author: MGW
> #2012
> import os, datetime, sys, arcpy, xlrd
> from arcpy import env
> submission = "Rev.mdb"
> env.workspace = "C:/temp/"+submission+"/Water"
>
> #Get Submission totals
> fclist = sorted(arcpy.ListFeatureClasses("*"))
> for fc in fclist:
> print fc+"="+str(arcpy.GetCount_management(fc).getOutput(0))
>
> print "Complete"
> raw_input("Press ENTER to close this window")
>
> Output Generated
> WATER_Net_Junctions=312
> WS_Hyd=484
> WS_Mains=2752
> WS_Node=4722
> WS_Vlvs=1078
> WS_WatLats=3661
> WS_WatMtrs=3662
> WTRPLANTS_points=0
> WTRPUMPSTA_points=0
> WTRTANKS=0
> WTR_ARV=10
> WTR_MISC=0
> Complete
> Press ENTER to close this window
>
> #Get Submission totals
> fclist = sorted(arcpy.ListFeatureClasses("*"))
> for fc in fclist:
> fc=str(arcpy.GetCount_management(fc).getOutput(0))
> #TEST
> print WS_Hyd
>
There's no variable WS_Hyd, so what did you expect it to do? Do you
want to be able to fetch the values by name that were printed above? if
so, I'd suggest a dict, not a list. Lists don't have names for each
element, just indices.
>
>
> print "Complete"
> raw_input("Press ENTER to close this window")
>
> Output Generated
> Traceback (most recent call last):
> File "C:\Documents and Settings\mattheww\Desktop\Copy of QAQCexce_2.py",
> line 14, in
> print WS_Hyd
> NameError: name 'WS_Hyd' is not defined
As a very rough start, perhaps you could try something like this.
Remember i don't have the docs, so the only clue I've got is the stuff
you printed from the first loop.
table = {}
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
table[fc] = +str(arcpy.GetCount_management(fc).getOutput(0))
Now, if you want to print the value for WS_Hyd, it should be available as
print "value = ", table["WS_Hyd"]
If you're sufficiently advanced, i could suggest a class-based solution
where you'd access items by
mytable.WS_Hyd
But if you're not yet familiar with class definition and attributes and
such, we'd better not go there.
--
DaveA
--
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Re: Defining features in a list
Dave- By features I was refering to items in the list. For background the arcpy module is used for geoprocessing of geographic information. I'm using my script to get totals for features in a dataset that I receive on a regular basis- for example total number of hydrants, total number of hydrants with null or missing attributes, and total number of hydrants with outlining attributes. I am experienced particularly with the arcpy module and I am trying deligently to become more experienced with Python in general. My goal is to fetch values by name and then print output by name. print WS_Hyd and then see "484". I have some experience with class definition but a dictionary might be the way to go. I was understanding the response of the Arcpy module but hadn't understood why the list wasn't being defined in my previous loop statement. I appreciate the response. I will look into dict if you have a class definition suggestion I will run with that. Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Defining features in a list
M Whitman wrote:
Good Morning,
I have been recently trying to define all of the features in a list but have
been running into errors. I would like to define the features similar to the
following print statement. Any advice would be appreciated. I'm trying to
transition my output from a text file to excel and if I can loop through my
lists and define them that transition will be cleaner.
Many Thanks,
-Matt
#Author: MGW
#2012
import os, datetime, sys, arcpy, xlrd
from arcpy import env
submission = "Rev.mdb"
env.workspace = "C:/temp/"+submission+"/Water"
#Get Submission totals
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
print fc+"="+str(arcpy.GetCount_management(fc).getOutput(0))
print "Complete"
raw_input("Press ENTER to close this window")
Output Generated
WATER_Net_Junctions=312
WS_Hyd=484
WS_Mains=2752
WS_Node=4722
WS_Vlvs=1078
WS_WatLats=3661
WS_WatMtrs=3662
WTRPLANTS_points=0
WTRPUMPSTA_points=0
WTRTANKS=0
WTR_ARV=10
WTR_MISC=0
Complete
Press ENTER to close this window
#Get Submission totals
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
fc=str(arcpy.GetCount_management(fc).getOutput(0))
#TEST
print WS_Hyd
print "Complete"
raw_input("Press ENTER to close this window")
Output Generated
Traceback (most recent call last):
File "C:\Documents and Settings\mattheww\Desktop\Copy of QAQCexce_2.py", line 14,
in
print WS_Hyd
NameError: name 'WS_Hyd' is not defined
I'm not sure I've understood everything, is this something you're
searching for:
fcDict = dict([(str(fc),
str(arcpy.GetCount_management(fc).getOutput(0))) ) for fc in
sorted(arcpy.ListFeatureClasses("*")) ])
print fcDict
print fcDict['WS_Hyd']
This is difficult to read because of the online statement, but it does
basically the following pseudo code:
fcDict = dict([(feature.name, feature.value) for feature in featureList ])
Cheers,
JM
--
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Re: Defining features in a list
On 09/07/2012 11:21 AM, M Whitman wrote:
> Dave- By features I was refering to items in the list. For background the
> arcpy module is used for geoprocessing of geographic information. I'm using
> my script to get totals for features in a dataset that I receive on a regular
> basis- for example total number of hydrants, total number of hydrants with
> null or missing attributes, and total number of hydrants with outlining
> attributes.
>
> I am experienced particularly with the arcpy module and I am trying
> deligently to become more experienced with Python in general. My goal is to
> fetch values by name and then print output by name. print WS_Hyd and then see
> "484". I have some experience with class definition but a dictionary might
> be the way to go. I was understanding the response of the Arcpy module but
> hadn't understood why the list wasn't being defined in my previous loop
> statement.
There is a list fclist being defined, just before the loop. But that
list contains the names of the "features" not the values. So if you
wanted, you could make a second list containing the values, or you could
even make a list containing tuples with name & value. But assuming
there's no particular ordering you care about, that's what a dictionary
is good at.
In either case that loop is not creating extra variables with names like
WS_Hyd. Creating variables with arbitrary names from data can only be
done with code that's dangerous and prone to injection attacks. You can
avoid the problem by putting them in some namespace, either a
dictionary, or a namedtuple, or a custom class.
> I appreciate the response. I will look into dict if you have a class
> definition suggestion I will run with that. Thanks
Anyway, once you have the dictionary, you can indeed work on the values
in it, in various ways.
table = {}
fclist = sorted(arcpy.ListFeatureClasses("*"))
for fc in fclist:
table[fc] = +str(arcpy.GetCount_management(fc).getOutput(0))
Now you can use your captured data to do further processing. Simplest example
printing. Suppose order doesn't matter:
for key in table.iterkeys():
print key, "=", table[key]
You could also do this as:
for key, value in table.iteritems():
print key, "=", value
If you want them in the original order, you can use your fclist, which is a
list of keys:
for key in fclist:
print key, "=", table[key]
And of course if you want any particular one, you can do
print table["WS_hyd"]
Note that in the last case, if you typed the literal key wrong, or if the arcpy
removed or renamed one of the keys, you'd get an exception there. To avoid
that, you might do something like:
key = "WS_hyd"
if key in table:
print table[key]
--
DaveA
--
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Re: Division help in python
Ramyasri Dodla wrote: Hi All, I am brand new to python. checking over basic stuff. I came across the problem while doing so. If any body aware of the problem, kindly respond me. >>> 5/10 0 >>> - 5/10 -1 The second case also should yield a 'zero' but it is giving a -1 Why should it yield 'zero' ? The definition of the euclidean division : (http://en.wikipedia.org/wiki/Euclidean_division) a = b*q +r with 0≤ r < |b| With the constraint of r being a positive integer, the couple (q, r) is unique: with a=-5, b=10 -5 = 10*-1 + 5 (q=-1, r=+5) Note that for the strict Euclidean division, I mean the one allowing r to be negative, then -5 = 10*0 - 5 (q=0, r=-5) is also valid, but I there's still no reason to state that it SHOULD be prefered over the other solution. The uniqueness of the solution for the 1st definition is probably what makes python yield -1 instead of 0. Cheers, JM -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitshifts and "And" vs Floor-division and Modular
On Sep 7, 9:32 am, Paul Rubin wrote: > rusi writes: > > On an 8086/8088 a MUL (multiply) instruction was of the order of 100 > > clocks ... On most modern processors (after the pentium) the > > difference has mostly vanished. I cant find a good data sheet to > > quote though > > See http://www.agner.org/optimize/: Hey Thanks! Seems like a nice resource! How on earth does he come up with the data though, when Intel does not publish it? -- http://mail.python.org/mailman/listinfo/python-list
Re: Bitshifts and "And" vs Floor-division and Modular
On 09/07/2012 12:59 PM, rusi wrote: > On Sep 7, 9:32 am, Paul Rubin wrote: >> rusi writes: >>> On an 8086/8088 a MUL (multiply) instruction was of the order of 100 >>> clocks ... On most modern processors (after the pentium) the >>> difference has mostly vanished. I cant find a good data sheet to >>> quote though >> See http://www.agner.org/optimize/: > Hey Thanks! Seems like a nice resource! How on earth does he come up > with the data though, when Intel does not publish it? As he says on the home page, he measured the data himself. Unclear how repeatable such data may be, either due to environment or to multiple versions of the processor, and from two vendors. -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing dll
On Sep 7, 5:16 am, Chris Angelico wrote: > On Fri, Sep 7, 2012 at 1:44 AM, Helpful person wrote: > > FYI > > > My Python version is 2.5.4 > > You may wish to upgrade, that's quite an old version. Unless > something's binding you to version 2.x, I would strongly recommend > migrating to 3.2 or 3.3. > > ChrisA Upgrading is not possible due to the large number of programs using the early version. -- http://mail.python.org/mailman/listinfo/python-list
Reusable (local) Modules
I'm relatively new to Python (coming from strong C and Smalltalk backgrounds). I've written a couple of relatively small apps (one or two .py files). I'm using PyCharm (I love it). I'm curious what the pythonic approach is to creating your own reusable modules. Any tutorials or high level explanations, or detailed, much appreciated. For example, I have a small module called valvenumbers.py. It's a family of functions that we use to do a variety of things with the serial numbers we attach to some of our products. Now I'm making a little desktop app using wxpython, and I want to use (import) that module. Using PyCharm, I have two separate projects in sibling directories. And there's another separate command line tool that wants to do the same. Currently, I just place a symlink to the valvenumbers.py, local to the directory of these apps. This seems like "the quickest thing that could possibly work", but I'm assuming there's a more pythonic way to approach this general problem. TIA! Travis Griggs "Simplicity is the ultimate sophistication." -- Leonardo Da Vinci -- http://mail.python.org/mailman/listinfo/python-list
Re: Reusable (local) Modules
On 09/07/2012 01:56 PM, Travis Griggs wrote: > I'm relatively new to Python (coming from strong C and Smalltalk > backgrounds). I've written a couple of relatively small apps (one or two .py > files). I'm using PyCharm (I love it). > > I'm curious what the pythonic approach is to creating your own reusable > modules. Any tutorials or high level explanations, or detailed, much > appreciated. > > For example, I have a small module called valvenumbers.py. It's a family of > functions that we use to do a variety of things with the serial numbers we > attach to some of our products. Now I'm making a little desktop app using > wxpython, and I want to use (import) that module. Using PyCharm, I have two > separate projects in sibling directories. And there's another separate > command line tool that wants to do the same. Currently, I just place a > symlink to the valvenumbers.py, local to the directory of these apps. This > seems like "the quickest thing that could possibly work", but I'm assuming > there's a more pythonic way to approach this general problem. > > TIA! > > Travis Griggs > "Simplicity is the ultimate sophistication." -- Leonardo Da Vinci > import sys print sys.path This will show you your path for imports. The actual directories change by default with different python versions, but one of them will be suitable for putting new modules to be imported. Naturally, you don't want to add to the place where the stdlib is placed, but some of those are normal writable directories. -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Reusable (local) Modules
On 09/07/2012 01:56 PM, Travis Griggs wrote: > I'm relatively new to Python (coming from strong C and Smalltalk > backgrounds). I've written a couple of relatively small apps (one or two .py > files). I'm using PyCharm (I love it). > > I'm curious what the pythonic approach is to creating your own reusable > modules. Any tutorials or high level explanations, or detailed, much > appreciated. > > For example, I have a small module called valvenumbers.py. It's a family of > functions that we use to do a variety of things with the serial numbers we > attach to some of our products. Now I'm making a little desktop app using > wxpython, and I want to use (import) that module. Using PyCharm, I have two > separate projects in sibling directories. And there's another separate > command line tool that wants to do the same. Currently, I just place a > symlink to the valvenumbers.py, local to the directory of these apps. This > seems like "the quickest thing that could possibly work", but I'm assuming > there's a more pythonic way to approach this general problem. > > TIA! > > Travis Griggs > "Simplicity is the ultimate sophistication." -- Leonardo Da Vinci > import sys print sys.path This will show you your path for imports. The actual directories change by default with different python versions, but one of them will be suitable for putting new modules to be imported. Naturally, you don't want to add to the place where the stdlib is placed, but some of those are normal writable directories. There are also several ways to add your own directories to that path, but maybe you don't need that complexity yet. I'm sure others will be able to be more specific. -- DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Division help in python
On 07.09.12 15:53, Ramyasri Dodla wrote: > I am brand new to python. checking over basic stuff. I came across the > problem while doing so. If any body aware of the problem, kindly respond me. > > >>> 5/10 > 0 > >>> - 5/10 > -1 > > The second case also should yield a 'zero' but it is giving a -1 http://python-history.blogspot.com/2010/08/why-pythons-integer-division-floors.html -- http://mail.python.org/mailman/listinfo/python-list
Using Raw Data in NLTK
Dear Group, I am trying to use NLTK and its statistical classifiers. The system is working fine but I am trying to use my own data, instead of things like, from nltk.corpus import brown from nltk.corpus import names If any one can kindly guide me up. Thanks in Advance, Regards, Subhabrata. -- http://mail.python.org/mailman/listinfo/python-list
Re: ctypes - python2.7.3 vs python3.2.3
In <9a74$503e88dd$546bb230$30...@cache80.multikabel.net> Jan Kuiken
writes:
> >> uint32_t myfunction (char ** _mydata)
> >> {
> >> char mydata[16];
> >
> >> strcpy(mydata, "Hello Dude!");
> >
> >> *_mydata = mydata;
> >
> >> return 0;
> >> }
> >
> > mydata is an auto variable, which goes out of scope when myfunction()
> > exits. *_mydata ends up pointing to garbage.
> I'm not completely sure, but i think this can be solved by using:
> static char mydata[16];
That will solve the immediate problem, however it makes myfunction()
non-reentrant.
> (Btw.: I don't know why you use char ** _mydata, i would use
> char * _mydata, but then again, i'm not very familiar with
> ctypes)
He uses char **_mydata because he wants myfunction()'s caller to see the
new value of _mydata, which it wouldn't if it were just char *_mydata.
--
John Gordon A is for Amy, who fell down the stairs
gor...@panix.com B is for Basil, assaulted by bears
-- Edward Gorey, "The Gashlycrumb Tinies"
--
http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
On 2012-09-07, Steven D'Aprano wrote: > > > After further thought, and giving consideration to the arguments given by > people here, I'm now satisfied to say that for equal-length strings, > string equality is best described as O(N). > > 1) If the strings are equal, a == b will always compare all N >characters in each string. > > 2) If the strings are unequal, a == b will *at worst* compare >all N characters. > > 3) Following usual practice in this field, worst case is the >one which conventionally is meant when discussing Big Oh >behaviour. See, for example, "Introduction To Algorithms" >by Cormen, Leiserson and Rivest. Would you say, then, that dict insertion is O(N)? > > Also of some interest is the best case: O(1) for unequal strings (they > differ at the first character) and O(N) for equal strings. > > Also of interest is the case that has caused the majority of the > discussion, the average case. I am now satisfied that the average number > of comparisons for unequal strings is O(1). To be precise, it is bounded > below by 1 comparison (you always have to compare at least one pair of > characters) and bounded above by 2 comparisons. I find this idea of separating into the comparison of equal strings versus the comparison of unequal strings rather odd. If the strings you compare come from a distribution where they are guaranteed to be equal (or unequal) then you can just use the O(0) comparison method. Since string comparison is only useful if the strings can be equal or unequal, the average case depends on how often they are equal/unequal as well as the average complexity of both. For random strings the frequency of equal strings decreases very fast as N increases so that the comparison of random strings is O(1). > > (I'm talking about the average here -- the actual number of comparisons > can range all the way up to N, but the average is <= 2.) > > If I've done the maths right, the exact value for the average is: > > ((M-1)*sum( (N-i)*M**i for i in range(0, N) ) + N)/(M**N) I'm not sure where the extra N comes from ^ but otherwise good. I would have written that as: (1 - p) * sum(i * p**(i-1) for i in range(1, N+1)) where p is the probability of a match (1/M for M equally likely characters) or in closed form: ⎛ N ⎞ ⎝1 - p ⋅(1 + N ⋅(1 - p))⎠ ─ 1 - p > > for random strings of length N taken from an alphabet of size M. > > For M = 2, that average approaches but never exceeds 2 as N increases; > for M = 3, the average approaches 1.5, for M = 4 it approaches 1.333... > and so forth. It approaches 1 / (1 - p) or, if you prefer: M / (M - 1) Oscar -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
On 2012-09-07, Oscar Benjamin wrote: > On 2012-09-07, Steven D'Aprano wrote: >> > > Since string comparison is only useful if the strings can be equal or unequal, > the average case depends on how often they are equal/unequal as well as the > average complexity of both. For random strings the frequency of equal strings > decreases very fast as N increases so that the comparison of random strings is > O(1). > >> >> (I'm talking about the average here -- the actual number of comparisons >> can range all the way up to N, but the average is <= 2.) >> >> If I've done the maths right, the exact value for the average is: >> >> ((M-1)*sum( (N-i)*M**i for i in range(0, N) ) + N)/(M**N) > > I'm not sure where the extra N comes from ^ but otherwise good. Ok, I see it's for the case where they're equal. Oscar -- http://mail.python.org/mailman/listinfo/python-list
Re: Dynamically scheduling Cron Jobs for Python Scripts.
Miki Tebeka wrote: >> I want to re run the script at that schedule time to send me a email. > > Calculate how much time until the meeting. And spawn the script that will > sleep that amount of time and then send email. And if the process gets interrupted in the meantime (e.g. because of reboot)? Ciao, Michael. -- http://mail.python.org/mailman/listinfo/python-list
Re: Using Raw Data in NLTK
On 9/7/2012 3:02 PM, subhabangal...@gmail.com wrote: Dear Group, I am trying to use NLTK and its statistical classifiers. The system is working fine but I am trying to use my own data, instead of things like, from nltk.corpus import brown from nltk.corpus import names If any one can kindly guide me up. from mypack import mydata The important thing is that mydata have the proper format. I would think that the nltk docs have instructions for and examples of using personal data -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
With unequal strings/lists to match, it would seem that one would regex through the larger string/list with the shorter string, and piece by piece begin to match for partial percentage matches in relation to the longer iterative item. -- Best Regards, David Hutto *CEO:* *http://www.hitwebdevelopment.com* -- http://mail.python.org/mailman/listinfo/python-list
how to run python2.6 module with absolute imports stand alone
Hi, many of my modules contain following section at the end def main(): do_something() if __name__ == '__main__': main() This allows me to run some basic example code or some small test in a stand alone mode. My new modules contain following line at the beginning: from __future__ import absolute_import I like this: - It can reduce import name conflicts - and second it allows 'relative' imports like from .othermodule import funcname from ..mod_one_level_higher import fdfsd However If I try to run such a script from the command line it will now complain with ValueError: Attempted relative import in non-package Any tricks to work around this ??? The only idea, that I have is to have a script, that would take my modulename or path name as parameter, and try to import it and then call the main function of the imported module. Not very elegant, but probably functional. Thanks in advance for any other suggestions / ideas. -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
On Fri, Sep 7, 2012 at 5:59 PM, Dwight Hutto wrote: > With unequal strings/lists to match, it would seem that one would regex > through the larger string/list with the shorter string, and piece by piece > begin to match for partial percentage matches in relation to the longer > iterative item. > While iterating through the larger list character/item, one at a time, or arranging them in certain instances. > > -- > Best Regards, > David Hutto > *CEO:* *http://www.hitwebdevelopment.com* > > -- Best Regards, David Hutto *CEO:* *http://www.hitwebdevelopment.com* -- http://mail.python.org/mailman/listinfo/python-list
Re: how to run python2.6 module with absolute imports stand alone
On 07/09/2012 23:04, Gelonida N wrote: Hi, many of my modules contain following section at the end def main(): do_something() if __name__ == '__main__': main() This allows me to run some basic example code or some small test in a stand alone mode. My new modules contain following line at the beginning: from __future__ import absolute_import I like this: - It can reduce import name conflicts - and second it allows 'relative' imports like from .othermodule import funcname from ..mod_one_level_higher import fdfsd However If I try to run such a script from the command line it will now complain with ValueError: Attempted relative import in non-package Any tricks to work around this ??? The only idea, that I have is to have a script, that would take my modulename or path name as parameter, and try to import it and then call the main function of the imported module. Not very elegant, but probably functional. Thanks in advance for any other suggestions / ideas. I hope this helps http://stackoverflow.com/questions/3616952/how-to-properly-use-relative-or-absolute-imports-in-python-modules -- Cheers. Mark Lawrence. -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
On Fri, 07 Sep 2012 19:10:16 +, Oscar Benjamin wrote: > On 2012-09-07, Steven D'Aprano > wrote: >> >> >> After further thought, and giving consideration to the arguments given >> by people here, I'm now satisfied to say that for equal-length strings, >> string equality is best described as O(N). >> >> 1) If the strings are equal, a == b will always compare all N >>characters in each string. >> >> 2) If the strings are unequal, a == b will *at worst* compare >>all N characters. >> >> 3) Following usual practice in this field, worst case is the >>one which conventionally is meant when discussing Big Oh behaviour. >>See, for example, "Introduction To Algorithms" by Cormen, Leiserson >>and Rivest. > > Would you say, then, that dict insertion is O(N)? Pedantically, yes. But since we're allowed to state (or even imply *wink*) whatever assumptions we like, we're allowed to assume "in the absence of significant numbers of hash collisions" and come up with amortized O(1) for dict insertions and lookups. (Provided, of course, that your computer has an infinite amount of unfragmented memory and the OS never starts paging your dict to disk. Another unstated assumption that gets glossed over when we talk about complexity analysis -- on real world computers, for big enough N, *everything* is O(2**N) or worse.) Big Oh analysis, despite the formal mathematics used, is not an exact science. Essentially, it is a way of bringing some vague order to hand- wavy estimates of complexity, and the apparent mathematical rigour is built on some awfully shaky foundations. But despite that, it actually is useful. Coming back to strings... given that in any real-world application, you are likely to have some string comparisons on equal strings and some on unequal strings, and more importantly you don't know which are which ahead of time, which attitude is less likely to give you a nasty surprise when you run your code? "I have many millions of 100K strings to compare against other 100K strings, and string comparisons are O(1) so that will be fast." "I have many millions of 100K strings to compare against other 100K strings, and string comparisons are O(N) so that will be slow, better find another algorithm." Remember too that "for small enough N, everything is O(1)". Getting hung up on Big Oh is just as much a mistake as ignoring it completely. > I find this idea of separating into the comparison of equal strings > versus the comparison of unequal strings rather odd. If the strings you > compare come from a distribution where they are guaranteed to be equal > (or unequal) then you can just use the O(0) comparison method. If you know that they're (un)equal, you don't need to call == at all. If you know that "most" strings will be unequal, then you might be justified in treating comparisons as O(1) "most of the time" and not stress about the occasional slow call. But of course most of the time you don't know this, which is why it is appropriate to treat string comparisons as O(N) rather than O(1), since that's the upper bound. > Since string comparison is only useful if the strings can be equal or > unequal, the average case depends on how often they are equal/unequal as > well as the average complexity of both. For random strings the frequency > of equal strings decreases very fast as N increases so that the > comparison of random strings is O(1). But that is not an upper bound, and Big Oh analysis is strictly defined in terms of upper bounds. >> (I'm talking about the average here -- the actual number of comparisons >> can range all the way up to N, but the average is <= 2.) >> >> If I've done the maths right, the exact value for the average is: >> >> ((M-1)*sum( (N-i)*M**i for i in range(0, N) ) + N)/(M**N) > > I'm not sure where the extra N comes from ^ but otherwise good. The extra N comes from the case where you compare string S with itself, which takes exactly N comparisons. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Comparing strings from the back?
Why don' you just time it,eit lops through incrementing thmax input/ -- Best Regards, David Hutto *CEO:* *http://www.hitwebdevelopment.com* -- http://mail.python.org/mailman/listinfo/python-list
Re: Python newbie here! No module named settings
>> I was trying to use Python wrapper for Google Charts API and was >> tweaking the examples. >> https://github.com/gak/pygooglechart/raw/master/examples/pie.py >> >> This is the script which I was trying. >> >> And the python interpreter gives the following error: >> import settings >> ImportError: No module named settings >> >> I installed Django as well before this (if its causing the problem, >> dunno) I searched Google for "django import settings" and found a few links that might be helpful. -- http://mail.python.org/mailman/listinfo/python-list
