Re: [Edu-sig] teaching python using turtle module
Hello Brian,
I think the most natural use of the if statement (using turtle
graphics) occurs in recursive functions drawing trees,
fractals and the like. This is well known from Logo, where
recursion is the canonical way of doing repetitions. (But
note, that Logo has tail recursion optimizaton!)
If you are not yet ready to use recursion with your students,
probably many of the problems coming to your mind that need
the examination of conditions can be solved better by using
a conditional loop (i. e. a while -loop in Python) than by
using mere if statements.
That is not the case however, if you have to perform actions in
the body of a loop, that depend on the current situation.
I did a quick search in my repository of examples and found
a fairly short and simple script that demonstrates, what I mean:
a drunken turtle collecting coins (or whatever) on its random walk.
# Python script using turtle graphics
from turtle import Screen, Turtle
from random import randint
s = Screen()
s.setup(560,560)
s.title("A drunken turtle collecting ...")
s.tracer(False)
writer = Turtle(visible=False)
writer.penup()
writer.goto(0, -275)
coins = []
for i in range(-4,5):
for j in range(-4, 5):
if i == j == 0:
continue
c = Turtle(shape="circle")
c.color("", "orange")
c.shapesize(0.5)
c.goto(40*i, 40*j)
coins.append(c)
s.tracer(True)
DRUNKENNESS = 45
t = Turtle(shape="turtle")
t.color("black","")
points = 0
while abs(t.xcor()) < 200 and abs(t.ycor()) < 200:
t.forward(5)
t.right(randint(-DRUNKENNESS, DRUNKENNESS))
found = None
for c in coins:
if t.distance(c) < 10:
found = c
break
if found:
found.hideturtle()
coins.remove(found)
t.shapesize(1+points/5., outline=1+points)
points += 1
writer.write("{0} points".format(points),
align="center", font=('Arial', 24, 'bold'))
## End of script
You can see a screenshot of a run of this script here:
http://www.dropbox.com/gallery/2016850/1/TurtleCollector?h=6b370a
The script could be expanded in several ways, e. g. for
doing statistical investigations or examinig how the
result depends on different parameters like drunkenness etc.
Or you distribute the coins randomly ... Does that alter
the average "harvest"?
Just a suggestion ...
Regards,
Gregor
Brian Blais schrieb:
Hello,
I was just playing with the turtle module, and thought it was an
interesting way to augment the introduction to python (I teach college
students, who haven't had any programming). It's a great way to
introduce functions, for-loops, and general program structures.
After a bit of playing, I realized that I couldn't think of many
examples which use turtle with conditional structures (if- and while-
statements), or functions that return values, as opposed to
"procedures" like:
def square(length):
forward(length)
right(90)
forward(length)
right(90)
forward(length)
right(90)
forward(length)
right(90)
If-statements could possibly be used with some sort of random behavior
(if rand()<0.5 ...). Are there any other situations, using turtle,
that these structures would be natural?
thanks,
Brian Blais
--
Brian Blais
bbl...@bryant.edu
http://web.bryant.edu/~bblais
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Re: [Edu-sig] teaching python using turtle module
kirby urner schrieb:
I'm glad turtle graphics intersected my thinking re extended precision
decimals (Decimal type) on edu-sig just now.
I've updated my tmods.py to contain a turtle rendering the plane-net of a T-mod:
http://www.4dsolutions.net/ocn/python/tmod.py (runnable source)
http://www.flickr.com/photos/17157...@n00/4147429781/ (GUI view)
Nice tiny app! Albeit not an example for using the if statement ;-)
Just to show you how turtle.py enables you to implement this
using quite different approaches to doing geometry, I'd like to add
two more implementations.
Besides you may notice that these do not rely on rather complicated
calculations of distances and angles, using the Pythagorean theorem
and trigonometrics but only on a few more fundamental properties of
the figure.
# Version 2 - using coordinate geometry without coordinates ;-)
# a different implementation for Kirby's "Plane Net for T-module"
from turtle import *
from math import sqrt
PHI = (sqrt(5)-1)/2
def planeNet(h=500):
setup(560,560)
title("Plane Net for T-module")
penup()
back(h/2); left(90); back(h/2); right(90)
pendown()
forward(h); left(90)
forward(h*PHI); A = pos(); forward(h-h*PHI); left(90)
forward(h*PHI); B = pos(); forward(h-h*PHI); left(90)
forward(h); C = pos()
for P in A, B, C:
goto(P)
# Version 3 - stamping simple transforms of the shape of
# an isosceles rectangular triangle:
from turtle import Screen, Turtle
from math import sqrt
GOLDEN_RATIO = (sqrt(5)-1)/2
def planeNet(h=500.0, phi=GOLDEN_RATIO):
s = Screen(); s.setup(560,560); s.title("Plane Net for T-module")
s.register_shape("recttriangle", ((0, 0), (h, 0), (0, h)))
designer = Turtle(shape="recttriangle")
designer.color("black","")
designer.penup()
designer.goto(-h/2, h/2)
for width, height in ((1, 1-phi), (phi, 1-phi), (phi, 1)):
designer.shapesize(width, height)
designer.stamp()
designer.forward(h)
designer.right(90)
designer.hideturtle()
Hoping, you will find this a bit interesting,
best regards
Gregor
Here's the graphical output:
http://www.flickr.com/photos/17157...@n00/4148139184/in/photostream/
(Python 3.1)
If you actually wanna fold the T, you need to snip off the cap and
reverse it, per this diagram:
http://www.rwgrayprojects.com/synergetics/s09/figs/f86515.html
120 of them, 60 folded left, 60 folded right, all of volume 1/24, make
the volume 5 rhombic triacontahedron.
http://www.rwgrayprojects.com/synergetics/s09/figs/f86419.html
If you blow up the volume by 3/2, to 7.5, the radius becomes phi /
sqrt(2) -- what we're showing with Decimals.
The reason this seems unfamiliar is the unit of volume is the
tetrahedron formed by any four equi-radiused balls in inter-tangency.
I'm spinning this as Martian Math these days, yakking on
math-thinking-l about it, learned it from Bucky Fuller, Dave Koski et
al.
Kirby
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ANN: Python's turtle module: collection of examples + demoViewer
Hi all, A few days ago I've created a repository of turtle graphics demos/applications, that use Python's new turtle module. You can find it at at google code: http://python-turtle-demo.googlecode.com There are two versions of the collection: one for use with Python 3.1 and one for use with Python 2.5 / 2.6. The latter contains a *** backport of version 1.1 of the turtle module *** *** (from Python 3.1) to Python 2.5 / 2.6 *** Among others it contains all the examples I have demonstrated at Pycon 2009 and at EuroPython 2009. Moreover it contains the demoViewer (which is also in the source distribution of CPython) that lets you select the examples via a menu, display their source code and execute them in parallel. If you are interested to amend some of these examples, add some explanatory material or contribute additional examples, please tell me so I could add you as a committer to the project. I'd be glad to expand the repository whith interesting examples and applications using the turtle module. If you have questions concerning the examples, feel free to ask here or ask me directly via my email-address. I hope this collection will prove to be useful. Best regards, Gregor P.S.: I tried to announce it at comp.lang.python.announce but for some unknown reason it was not accepted there -- http://mail.python.org/mailman/listinfo/python-list
Re: Announcing PythonTurtle
cool-RR schrieb: Hello, I wanted to announce that I have just released my little side project, PythonTurtle. Here is its website: http://pythonturtle.com Its goal is to be the lowest-threshold way to learn (or teach) Python. You can read more about it and download it on the website. Ram. Hi Ram, that's indeed a nice starting point for kids to doing turtle graphics, although currently it seems to implement only a very small subset of Python's turtle module's capabilities, even less than those of the old turtle module (that shipped with Python upto 2.5). Moreover I have to complain that you decided to use different commands for the turtle's actions - go instead of forward, turn instead of left and right etc. First I think left and right are more intuitive than turn as they do not need negative angles as arguments, which might matter for young children. Also I cannot see the advantage of cammands like visible() or invisible() over showturtle() and hideturtle() But second even kids - when learning how to program - will arrive at a point where it's no more problem to use an editor like IDLE so they could easily switch to Python's turtle module. That would be even easier if they had not to learn a new command set. Moreover a learning environment like PythonTurtle needs something like an editor - at least a simple one - in order to create programs that can be run repeatedly. Coding, that's creating programs - not only issuing a sequence of cammands interactively. It would be certainly a good thing if one had a similar environment using Tkinter, preferably also as part of the standard distribution of Python accompanying the turtle module. I think it should not be that difficult to create a GUI of this sort combining IDLE's shell window, its editor and turtle.py. Alas, at the moment I'm too busy with some othr work to start a project like this. Perhaps someone else might be interested? I'd enjoy to join a team doing it. Finally I'd like to stress, that the aims of PythonTurtle and Python's turtle module are quite different - as one could grasp easily by trying out the collection of examples at python-turtle-demo.googlecode.com that I posted in another posting. Anyway they could very well complement one another in some more mature state of development. Best regards, Gregor -- http://mail.python.org/mailman/listinfo/python-list
Re: Announcing PythonTurtle
cool-RR schrieb: On Aug 4, 7:12 am, John Posner wrote: ... I would also venture to say a key-map ... If you're asking WHY I put it in a wxPython application, the answer is pretty much what "r" said: To make it like any other "over the counter" Windows application, making people feel more comfortable with it. Also, not requiring them to install Python+packages, but just PythonTurtle. Fortunately it's not necessary to install 'packages' to use Python's turtle module as it is one of it's 'batteries included'. And I think it's not so a bad idea to install Python if one want's to learn it, anyway. Regards, Gregor Ram. -- http://mail.python.org/mailman/listinfo/python-list
Re: Announcing PythonTurtle
cool-RR schrieb: Hi Ram, that's indeed a nice starting point for kids to doing turtle graphics, although currently it seems to implement only a very small subset of Python's turtle module's capabilities, even less than those of the old turtle module (that shipped with Python upto 2.5). ... A text editor would be a good feature for future versions. Regarding the naming of functions: I named them in the way that seemed best to me. You seem not to agree, you like the way your functions are named better, and there's little point in arguing over which convention is truly better. The convention I chose is the one that seemed ideal to me. I did consider naming the functions the same way you did for consistency, but I decided not to compromise the quality of PythonTurtle just to be compatible with a module that my users may not even use. That's the advantage of not developing for the standard library. In fact those elementary commands you use were present already in the old turtle module. When I decided to extend the old turtle module a primary requirement was that it remains 100% compatible to the old one. New versions of a module in the standard library must not break code of previous users of that module. In short: I did not name these functions but I had to use the names that already were there. Nevertheless I'd prefer left and right over turn even today, especially for kids as I argued before. Regards, Gregor It would be certainly a good thing if one had a similar environment using Tkinter, preferably also as part of the standard distribution of Python accompanying the turtle module. I think it should not be that difficult to create a GUI of this sort combining IDLE's shell window, its editor and turtle.py. Alas, at the moment I'm too busy with some othr work to start a project like this. Perhaps someone else might be interested? I'd enjoy to join a team doing it. I agree that it shouldn't be difficult; The question is whether someone will step up and do it. Finally I'd like to stress, that the aims of PythonTurtle and Python's turtle module are quite different - as one could grasp easily by trying out the collection of examples at python-turtle-demo.googlecode.com that I posted in another posting. Anyway they could very well complement one another in some more mature state of development. Best regards, Gregor Thank you for your feedback Gregor. Ram Rachum. -- http://mail.python.org/mailman/listinfo/python-list
Re: Overlap in python
Jay Bird schrieb:
Hi everyone,
I've been trying to figure out a simple algorithm on how to combine a
list of parts that have 1D locations that overlap into a non-
overlapping list. For example, here would be my input:
part name location
a 5-9
b 7-10
c 3-6
d 15-20
e 18-23
And here is what I need for an output:
part name location
c.a.b3-10
d.e 15-23
Suppose you have your data given as a dictionary:
data = {'a':(5,9),
'b':(7,10),
'c':(3,6),
'd':(15,20),
'e':(18,23)}
Then the following not particularly elegant
but very simple and straight forward
algorithm will solve your problem:
def values(key):
return set(range(data[key][0], data[key][1]+1))
keys = list(data.keys())
result = []
while keys:
k = [keys[0]]
keys = keys[1:]
v = values(k[0])
for l in keys[:]:
if v.intersection(values(l)):
v.update(values(l))
k.append(l)
keys.remove(l)
result.append((k,v))
# print(result) ## if you like
for k, v in result:
print(".".join(sorted(k)), "%d-%d" % (min(v), max(v)))
Regards,
Gregor
I've tried various methods, which all fail. Does anyone have an idea
how to do this?
Thank you very much!
Jay
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Re: Overlap in python
DuaneKaufman schrieb: On Aug 4, 1:15 pm, Jay Bird wrote: ... For instance the interval module found at: http://members.cox.net/apoco/interval/ can be put to use: Given your data above: part name location a 5-9 b 7-10 c 3-6 from interval import Interval a_int=Interval(5,9) b_int=Interval(7,10) c_int=Interval(3,6) a_int.overlaps(b_int) True a_int.overlaps(c_int) True b_int.overlaps(c_int) False As my proposed solution shows this approach can be done with on board means of Python (namely the set type). This would be quite different though, if you had floating point boundaries of the intervals. Regards, Gregor Duane -- http://mail.python.org/mailman/listinfo/python-list
Re: Overlap in python
Gregor Lingl schrieb: As my proposed solution shows this approach can be done with on board means of Python (namely the set type). This would be quite different though, if you had floating point boundaries of the intervals. ... or if the intgers involved were very big :-( Regards, Gregor Duane -- http://mail.python.org/mailman/listinfo/python-list
Re: Turtle Graphics are incompatible with gmpy
Mensanator schrieb:
I hadn't noticed this before, but the overhaul of Turtle Graphics
dating
back to 2.6 has been broken as far as gmpy is concerned.
I hadn't noticed because I usually have tracing turned off (tracing
off
takes 3-4 seconds, tracing on takes 6-7 minutes).
In 3.1, tracing is now a screen attribute, not a turtle atribute.
I have no idea why
tooter = turtle.Turtle()
tooter.tracer(False)
doesn't give me an error (I thought silent errors were a bad thing).
Hi,
on my machine I get:
Python 3.1 (r31:73574, Jun 26 2009, 20:21:35) [MSC v.1500 32 bit
(Intel)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> import turtle
>>> tooter = turtle.Turtle()
>>> tooter.tracer(False)
Traceback (most recent call last):
File "", line 1, in
tooter.tracer(False)
AttributeError: 'Turtle' object has no attribute 'tracer'
>>>
I'd like to help with your problem but I'd much better be
able to analyze it, if I had a version of your script,
which works as you intended with Python 2.5 and the old
turtle module. Could you please post it?
(The one you posted below uses some commands of the
turtle 2.6 module which are not present in 2.5, so it
doesn't run with Python 2.5)
Regards,
Gregor
Had to change to
tooter = turtle.Turtle()
tooter.screen.tracer(False) # tracer now a screen attribute
to turn tracing off in 3.1.
Naturally, having tracing on caused my program to crash. The 2.6
version
seemed to work, but only because turning off tracing as a turtle
attribute
works in 2.6.
So I turned it back on and it crashed too.
2.5 worked okay.
The reason is that code in turtle.py was chabged from
v2.5
if self._drawing:
if self._tracing:
dx = float(x1 - x0)
dy = float(y1 - y0)
distance = hypot(dx, dy)
nhops = int(distance)
to
v3.1
if self._speed and screen._tracing == 1:
diff = (end-start)
diffsq = (diff[0]*screen.xscale)**2 + (diff[1]
*screen.yscale)**2
nhops = 1+int((diffsq**0.5)/(3*(1.1**self._speed)
*self._speed))
Unfortunately, that calculation of nhops is illegal if diffsq is
an .mpf (gmpy
floating point). Otherwise, you get
Traceback (most recent call last):
File "K:\user_python26\turtle\turtle_xy_Py3.py", line 95, in
tooter.goto(the_coord)
File "C:\Python31\lib\turtle.py", line 1771, in goto
self._goto(Vec2D(*x))
File "C:\Python31\lib\turtle.py", line 3165, in _goto
nhops = 1+int((diffsq**0.5)/(3*(1.1**self._speed)*self._speed))
ValueError: mpq.pow fractional exponent, inexact-root
So when using gmpy, you have to convert the .mpz to int before calling
turtle
functions. (if tracing is on).
demo code (fixed code commented out)
import gmpy
## (even) hi|
##|
##lo (odd)
## or
##
## (even) lo
## |
## |
## hi (odd)
##
##
##
##
import turtle
tooter = turtle.Turtle()
tooter.hideturtle()
tooter.speed('fast')
turtle.update()
# make tracer false and it works
#tooter.screen.tracer(False) # tracer now a screen attribute
tooter.penup()
tooter.color('black')
s = ['1','0']
while len(s[0])<1:
s = [''.join(s), s[0]]
origin = [0,0]
if s[0] == '0':
tooter.goto(origin)
tooter.dot(1)
if s[1] == '0':
tooter.goto([1,0])
tooter.dot(1)
print(len(s[0]))
for i,j in enumerate(s[0]):
the_coord=[]
cur_root = gmpy.sqrt(i)
lo__root = gmpy.sqrt(i)**2
hi__root = ((gmpy.sqrt(i)+1)**2)
## cur_root = int(gmpy.sqrt(i))
## lo__root = int(gmpy.sqrt(i)**2)
## hi__root = int(((gmpy.sqrt(i)+1)**2))
if hi__root%2==0:
side = 'northeast'
else:
side = 'southwest'
elbow = (hi__root - lo__root)//2 + lo__root + 1
if i>= elbow:
side_len = i - elbow
elbow_plus = True
else:
side_len = elbow - i
elbow_plus = False
if side == 'northeast':
elbow_offset = [(gmpy.sqrt(elbow)-1)//2 +1,-((gmpy.sqrt(elbow)-1)//
2) +1]
else:
elbow_offset = [-((gmpy.sqrt(elbow)-1)//2 +1),((gmpy.sqrt
(elbow)-1)//2 +1)]
## if side == 'northeast':
##elbow_offset = [int((gmpy.sqrt(elbow)-1)//2 +1),-int(((gmpy.sqrt
(elbow)-1)//2) +1)]
## else:
##elbow_offset = [-int(((gmpy.sqrt(elbow)-1)//2 +1)),int
(((gmpy.sqrt(elbow)-1)//2 +1))]
elbow_coord = [origin[0]+elbow_offset[0],origin[1]+elbow_offset[1]]
if i != hi__root and i != lo__root:
if i == elbow:
the_coord = elbow_coord
else:
if elbow_plus:
if side == 'northeast':
the_coord = [elbow_coord[0]-side_len,elbow_coord[1]]
else:
the_coord = [elbow_coord[0]+side_len,elbow_coord[1]]
else:
if side == 'northeast':
the_coord = [elbow_coord[0],elbow_coord[1]+side_len]
else:
the_coord = [elbow_coord[0],elbow_coord[1]-side_len]
else:
if i % 2 == 0: # even square
n = gmpy.sqrt(i)//2 - 1
## n = int(gmpy.sqrt(i)//2) - 1
the_coord = [-n, -n-1]
else:
n = (gmpy.s
Re: Turtle Graphics are incompatible with gmpy
Steven D'Aprano schrieb: On Wed, 5 Aug 2009 03:49 pm Mensanator wrote: In 3.1, tracing is now a screen attribute, not a turtle atribute. I have no idea why tooter = turtle.Turtle() tooter.tracer(False) doesn't give me an error (I thought silent errors were a bad thing). What makes it an error? Do you consider the following an error? class Test: ... pass ... t = Test() t.tracer = 5 Perhaps you mean, it's an API change you didn't know about, and you wish to protest that Turtle Graphics made an incompatible API change without telling you? It didn't form 2.5 to 2.6 (at least not intentionally). But with the indroduction of the TurtleScreen class and the Screen class/object (singleton) a few of the turtle methods were also implemented as screen methods and as turtle methods declared deprecated (see docs of Python 2.6). These deprecated turtle methods do not occur as turtle methods any more in Python 3.x. Among them is the tracer method, which in fact does not control single turtle objects but all the turtles on a given screen. So there is an icompatibility beween 2.6 and 3.x But as far as I have understood, this doesn't concern the problem reported by mensator. Regards, Gregor Naturally, having tracing on caused my program to crash. It seg faulted or raised an exception? [...] Unfortunately, that calculation of nhops is illegal if diffsq is an .mpf (gmpy floating point). Otherwise, you get How does diffsq get to be a mpf? Are gmpy floats supposed to be supported? -- http://mail.python.org/mailman/listinfo/python-list
Re: Turtle Graphics are incompatible with gmpy
Mensanator schrieb:
It didn't form 2.5 to 2.6 (at least not intentionally). But with the
indroduction of the TurtleScreen class and the Screen class/object
(singleton) a few of the turtle methods were also implemented as screen
methods and as turtle methods declared deprecated (see docs of Python
2.6). These deprecated turtle methods do not occur as turtle methods any
more in Python 3.x.
More info.
Yes, there is no tracer attribute...when the object is created.
But watch this (Python 3.1):
import turtle
tooter = turtle.Turtle()
tooter.tracer
Traceback (most recent call last):
File "", line 1, in
tooter.tracer
AttributeError: 'Turtle' object has no attribute 'tracer'
tooter.hideturtle()
tooter.speed('fast')
turtle.update()
turtle.tracer
Now, after setting hide, speed, update, a tracer exists.
No,
>>> import turtle
>>> turtle.tracer
>>> help(turtle.tracer)
Help on function tracer in module turtle:
tracer(n=None, delay=None)
Turns turtle animation on/off and set delay for update drawings.
Optional arguments:
n -- nonnegative integer
delay -- nonnegative integer
If n is given, only each n-th regular screen update is really
performed.
(Can be used to accelerate the drawing of complex graphics.)
Second arguments sets delay value.)
Example:
>>> tracer(8, 25)
>>> dist = 2
>>> for i in range(200):
fd(dist)
rt(90)
dist += 2
>>>
The reason for this is, that the turtle module (the new one as well as
the old one) has a vers special design: The methods of class Turtle are
also available as functions (which are in fact methods calls of an
anonymous turtle). The same holds for the methods of TurtleScreen.
The intention behind this design is that you can use the module in an
OOP way as well as with procedural programming (especially for beginners).
When using objects I normally use
from turtle import Turtle, Screen
screen = Screen()
# that creates singleton object, the screen the turtle acts on
and I create as many turtles as I need from the Turtle class
So turtle.tracer() doesn't make sense anymore
Is that supposed to happen? That explains why there was no error
when I set the turtle attribute instead of the screen attribute.
You do not 'set the turtle attribute', you call the tracer function of
the turtle module
And, of course, setting the turtle attribute accomplishes nothing,
as actual tracing is controlled by the screen attribute as you say.
Among them is the tracer method, which in fact does not control single
turtle objects but all the turtles on a given screen.
So there is an icompatibility beween 2.6 and 3.x
But as far as I have understood, this doesn't concern the problem
reported by mensator.
Only that the problem is hidden when tracing is off, as the nhops
variable is never evaluated when trace is off.
Nevertheless I'd like to see a working Python 2.5 version of your script.
Regards,
Gregor
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Re: Turtle Graphics are incompatible with gmpy
Mensanator schrieb: On Aug 5, 5:31 pm, Mensanator wrote: I fixed this to produce the actual image I'm looking for instead of that stupid black square. All I did was use up() & dowm() in place of penup(), pendown() and replace dot(2) with forward(1). I'll be posting a followup report later. http://www.mensanator.com/mensanator/PythonTurtle/turtle.htm Hi Mansanator, Thanks for that thorough investigations. I hope I'll soon find time to study it in detail. I've just one idea, but I don't know if you might be intersted in it or if it's rewarding at all: What would be the results when using the old turtle module with Python 3.1 (it will certainly not run out of the box, but perhaps 2to3 might do it?) That would clarify the question if there is some impact of new division or some changes in Tkinter. Best regards, Gregor -- http://mail.python.org/mailman/listinfo/python-list
Re: Splitting a string into substrings of equal size
What is the pythonic way to do this ?
For my part, i reach to this rather complicated code:
# --
def comaSep(z,k=3, sep=','):
z=z[::-1]
x=[z[k*i:k*(i+1)][::-1] for i in range(1+(len(z)-1)/k)][::-1]
return sep.join(x)
# Test
for z in ["75096042068045", "509", "12024", "7", "2009"]:
print z+" --> ", comaSep(z)
Just if you are interested, a recursive solution:
>>> def comaSep(z,k=3,sep=","):
return comaSep(z[:-3],k,sep)+sep+z[-3:] if len(z)>3 else z
>>> comaSep("7")
'7'
>>> comaSep("2007")
'2,007'
>>> comaSep("12024")
'12,024'
>>> comaSep("509")
'509'
>>> comaSep("75096042068045")
'75,096,042,068,045'
>>>
Gregor
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Re: Splitting a string into substrings of equal size
What is the pythonic way to do this ?
For my part, i reach to this rather complicated code:
# --
def comaSep(z,k=3, sep=','):
z=z[::-1]
x=[z[k*i:k*(i+1)][::-1] for i in range(1+(len(z)-1)/k)][::-1]
return sep.join(x)
# Test
for z in ["75096042068045", "509", "12024", "7", "2009"]:
print z+" --> ", comaSep(z)
Just if you are interested, a recursive solution:
>>> def comaSep(z,k=3,sep=","):
return comaSep(z[:-3],k,sep)+sep+z[-3:] if len(z)>3 else z
>>> comaSep("7")
'7'
>>> comaSep("2007")
'2,007'
>>> comaSep("12024")
'12,024'
>>> comaSep("509")
'509'
>>> comaSep("75096042068045")
'75,096,042,068,045'
>>>
Gregor
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Re: Splitting a string into substrings of equal size
Emile van Sebille schrieb: On 8/14/2009 5:22 PM candide said... ... What is the pythonic way to do this ? I like list comps... >>> jj = '1234567890123456789' >>> ",".join([jj[ii:ii+3] for ii in range(0,len(jj),3)]) '123,456,789,012,345,678,9' >>> Emile Less beautiful but more correct: >>> ",".join([jj[max(ii-3,0):ii] for ii in range(len(jj)%3,len(jj)+3,3)]) '1,234,567,890,123,456,789' Gregor -- http://mail.python.org/mailman/listinfo/python-list
Re: getting the fractional part of a real?
Christian Heimes schrieb: Roy Smith schrieb: What's the best way to get the fractional part of a real? The two ways I can see are r % 1 and r = int(r), but both seem a bit hokey. Is there something more straight-forward that I'm missing, like fraction(r)? import math math.modf(1.5) (0.5, 1.0) Christian Or without the need to import something: >>> divmod(1.5, 1) (1.0, 0.5) >>> Gregor -- http://mail.python.org/mailman/listinfo/python-list
Re: Splitting a string into substrings of equal size
Mark Tolonen schrieb:
"Gregor Lingl" wrote in message
news:4a87036a$0$2292$91cee...@newsreader02.highway.telekom.at...
Emile van Sebille schrieb:
On 8/14/2009 5:22 PM candide said...
...
What is the pythonic way to do this ?
I like list comps...
>>> jj = '1234567890123456789'
>>> ",".join([jj[ii:ii+3] for ii in range(0,len(jj),3)])
'123,456,789,012,345,678,9'
>>>
Emile
Less beautiful but more correct:
>>> ",".join([jj[max(ii-3,0):ii] for ii in
range(len(jj)%3,len(jj)+3,3)])
'1,234,567,890,123,456,789'
Gregor
Is it?
jj = '234567890123456789'
",".join([jj[max(ii-3,0):ii] for ii in range(len(jj)%3,len(jj)+3,3)])
',234,567,890,123,456,789'
Schluck!
Even more ugly:
",".join([jj[max(ii-3,0):ii] for ii in
range(len(jj)%3,len(jj)+3,3)]).strip(",")
'234,567,890,123,456,789'
Gregor
At least one other solution in this thread had the same problem.
-Mark
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Re: Splitting a string into substrings of equal size
Simon Forman schrieb:
On Aug 14, 8:22 pm, candide wrote:
Suppose you need to split a string into substrings of a given size (except
possibly the last substring). I make the hypothesis the first slice is at the
end of the string.
A typical example is provided by formatting a decimal string with thousands
separator.
What is the pythonic way to do this ?
...
Thanks
FWIW:
def chunks(s, length=3):
stop = len(s)
start = stop - length
while start > 0:
yield s[start:stop]
stop, start = start, start - length
yield s[:stop]
s = '1234567890'
print ','.join(reversed(list(chunks(s
# prints '1,234,567,890'
or:
>>> def chunks(s, length=3):
i, j = 0, len(s) % length or length
while i < len(s):
yield s[i:j]
i, j = j, j + length
>>> print(','.join(list(chunks(s
1,234,567,890
>>> print(','.join(list(chunks(s,2
12,34,56,78,90
>>> print(','.join(list(chunks(s,4
12,3456,7890
Regards,
Gregor
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