🌐 Mailman 3 January 2005 - Tutor - python.org

How to calculate pi with this formula?
by Dick Moores April 14, 2005

April 14, 2005

Is it possible to calculate almost-pi/2 using the (24) formula on <http://mathworld.wolfram.com/PiFormulas.html> without using (23)? If it's possible, how about a hint? Recursion? Thanks, tutors. Dick Moores rdm(a)rcblue.com

6 12

Newbie question.
by Adriaan Louw March 4, 2005

March 4, 2005

Good day I'm totally new to Python. Wow, what a great language!!! I want to learn python as quick as possible, for web programming at first, and applications later on. Any leads? I have an xp windows and ms office machine. (I'm considering linux, but it's a bit daunting?) How do I run python scripts? Nothing happens when I double-click the filename, in IDLE I only get the code, and not what it does. I know that cgi-scripts must be called from html. I want to to use a python server for testing. Which is thebest, and how? Maybe my problem lies with directories? Sub-folders and paths. That's what I gather from the tutorial, but I have no success as yet. Even pygame, from Start>Programs>Examples, the games doesn't work. Sorry for all the questions, but I want to learn and grow. Thank you. Adriaan

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Proxy
by Ali Polatel March 4, 2005

March 4, 2005

is it possible to connect to somewhere through a proxy while using sockets module of Python to connect? If yes can you show me some basic examples? regards --------------------------------- Do you Yahoo!? Yahoo! Search presents - Jib Jab's 'Second Term'

2 1

Better structure?
by Jacob S. Feb. 4, 2005

Feb. 4, 2005

I think this thing is screaming for better structure, but previous attempts at using oop for it have failed. I think Derintegral is okay, I'm focusing on FunctionGrapher5.py--but you can comment on both. (To Johan Nilsson: I haven't had time to implement Simpson's rule instead of Reimann's sum yet... but I have gotten it to work faster anyway.) I will probably expand the code yet... Add extra things like find area between curve and x axis in interval [a,b]... Any suggestions are greatly appreciated. If you want the code to work on your machine, you'll need to have my Derintegral.py sys.path, obviously. #### Start of FunctionGrapher5.py ################### from __future__ import division from visual import * import Derintegral import os, random from math import * ja = 0 scenexdefault = 375 def start(): for objects in scene.objects: objects.visible = 0 scene.title = "Function Grapher by Jacob, Inc." scene.x = scenexdefault scene.visible=1 scene.exit=0 scene.userspin = 0 scene.range=(10,10,1) scene.background=(1,1,1) global xaxis global yaxis xaxis = curve(pos=[(100,0,0),(-100,0,0)],color=color.black) yaxis = curve(pos=[(0,100,0),(0,-100,0)],color=color.black) global radiusaxis global radiusaxis2 radiusaxis = curve(pos=[(-100,-100),(100,100)],color=color.black) radiusaxis2 = curve(pos=[(-100,100),(100,-100)],color=color.black) radiusaxis.visible = 0 radiusaxis2.visible = 0 start() d = 1 print """\ List of Commands: clear quit remove lines return lines gotl # (Graph One Tangent Line) w/optional x coordinate gatl # (Graph All Tangent Lines) w/optional step gonl # (Graph One Normal Line) w/optional x coordinate ganl # (Graph All Normal Lines) w/optional step Function Syntax: [y,x,or r] = function [range] ["s" followed by float for step] Brackets mean that it's not required. So, in effect, you don't have to type a function """ def graphit(type,f,range2,step): li = curve(color=color.blue) if type in ['y','x']: x = -15 radiusaxis.visible = 0 radiusaxis2.visible = 0 while -15 <= x <= 15: if eval(range2): try: a = f(x) if -15 <= a <= 15: if type == 'y': li.append(pos=(x,a,0)) elif type == 'x': li.append(pos=(a,x,0)) else: li = curve(color=color.blue) except: pass else: li = curve(color=color.blue) x = x+step elif type == 'r': exec "def m(t): return f(t)*cos(t)" exec "def n(t): return f(t)*sin(t)" t = 0 while 0 <= t <= 10*pi: if eval(range2): try: li.append(pos=(m(t),n(t),0)) except: li = curve(color=color.blue) t = t+step print 'Please type in functions in below. ' while 1: lists=[] y = raw_input(">") if y == 'clear': scene.visible=0 start() print "-"*36 continue elif y == 'quit': scene.visible = 0 del scene break elif y == 'remove lines': a = [radiusaxis,radiusaxis2,xaxis,yaxis] for x in a: x.visible = 0 d = 0 continue elif y == 'return lines': a = [radiusaxis,radiusaxis2,xaxis,yaxis] for x in a: x.visible = 1 d = 1 continue elif y.startswith('gatl'): try: step2 = float(y.lstrip("gatl ")) except: step2 = 0.5 x = -20 while -20 <=x<= 20: try: der = Derintegral.diffatpt(f,x) if abs(der)<=25: if type == 'y': curve(pos=[(-15,eval("der*(-15-x)+f(x)")),(15,eval("der*(15-x)+f(x)"))],color=color.red) else: curve(pos=[(eval("der*(-15-x)+f(x)"),-15),(eval("der*(15-x)+f(x)"),15)],color=color.red) except: pass x = x + step2 continue elif y.startswith('ganl'): try: step2 = float(y.lstrip("ganl ")) except: step2 = 0.5 x = -20 while -20 <=x<= 20: try: der = Derintegral.diffatpt(f,x) if abs(der)<=25: if type == 'y': curve(pos=[(-15,eval("(-1/der)*(-15-x)+f(x)")),(15,eval("(-1/der)*(15-x)+f(x)"))],color = color.red) else: curve(pos=[(eval("(-1/der)*(-15-x)+f(x)"),-15),(eval("(-1/der)*(15-x)+f(x)"),15)],color = color.red) except: pass x = x + step2 continue elif y.startswith('gotl'): try: x = float(y.lstrip('gotl ')) except: x = float(raw_input('What x coordinate do you want the tangent line at? ')) der = Derintegral.diffatpt(f,x) try: if abs(der)<= 25: if type == 'y': curve(pos=[(-15,eval("der*(-15-x)+f(x)")),(15,eval("der*(15-x)+f(x)"))],color=color.red) else: curve(pos=[(eval("der*(-15-x)+f(x)"),-15),(eval("der*(15-x)+f(x)"),15)],color=color.red) except: pass continue elif y.startswith('gonl'): try: x = float(y.lstrip('gonl ')) except: x = float(raw_input('What x coordinate do you want the tangent line at? ')) der = Derintegral.diffatpt(f,x) try: if abs(der)<= 25: if type == 'y': curve(pos=[(-15,eval("(-1/der)*(-15-x)+f(x)")),(15,eval("(-1/der)*(15-x)+f(x)"))],color=color.red) else: curve(pos=[(eval("(-1/der)*(-15-x)+f(x)"),-15),(eval("(-1/der)*(15-x)+f(x)"),15)],color=color.red) except: pass continue elif y.startswith('getpt'): y = y.lstrip("getpt ") if y: m = float(eval(y)) else: m = float(eval(raw_input("f(?) "))) try: print f(m) except ValueError: print "Math Domain Error" continue elif y == 'regraph': graphit(type,f,range2,step) continue if y.count(" = ") == 1: y = y.split(" = ") type = y[0].lower() y = y[1] y = y.replace("y","x") if type == 'r': defaultrange = '0<=t<=5*pi' y = y.replace('x','t') if d == 1: radiusaxis.visible = 1 radiusaxis2.visible = 1 else: defaultrange = '-15<=x<=15' else: type = 'y' defaultrange = '-15<=x<=15' y = y.split(" ",1) tempfunct = y.pop(0) if y: y = y[0] if y.count('st'): if y.startswith('st'): y = y.lstrip('st') step = float(y) else: y = y.split(" ") step = float(y.pop().lstrip('st')) y = " ".join(y) range2 = defaultrange else: range2 = y step = 0.005 else: range2 = defaultrange step = 0.005 y = tempfunct range2 = range2.replace('and','or') range2 = range2.replace(',','<=x<=') try: exec "def f(x): return %s" % y except: continue graphit(type,f,range2,step) ###### End of FunctionGrapher5.py ########### #### Start of Derintegral.py ########## from __future__ import division import psyco psyco.full() from math import * def diffatpt(funct,pt): """Return the derivative of a function at a specific point. """ sminc = 1e-10 x = pt+sminc y2 = funct(x) x2 = x x = pt-sminc y1 = funct(x) x1 = x slope = (y2-y1)/(x2-x1) return slope def defintegral(fofx,x,max1): total = 0 step = 1e-5 exec "def f(x): return %s" % fofx while x <= max1: try: total = total+f(x) except: pass x = x+step return abs(total*step) ######End of Derintegral.py ########## Like I said, any comments appreciated. Jacob Schmidt

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How to sum rows and columns of a matrix?
by Gregor Lingl Feb. 2, 2005

Feb. 2, 2005

Hi all of you, I'm representing a 4x4 matrix as a 16-element list, e.g. m=range(16) first 4 elements first row, second four elements second row etc. I want to sum rows and columns like i-th row: sum(m[4*i:4*i+4]) and ith column: sum(m[i::4]) This seems to be slow because of the formation of the slices. I wonder if there is a way using generators or generator-expressions (which I didn't study yet) to compute these sums without copying parts of the matrix to a new list. (I'd guess that there should exist some canonical generator for sequences, which produces their elements ..., maybe also for slices ?) All comments, hints, solutions are welcome. Regards, Gregor -- Gregor Lingl Reisnerstrasse 3/19 A-1030 Wien Telefon: +43 1 713 33 98 Mobil: +43 664 140 35 27 Autor von "Python für Kids" Website: python4kids.net

5 5

Append function
by kumar s Feb. 1, 2005

Feb. 1, 2005

Hello: In append function instead of appending one below the other can I append one next to other. I have a bunch of files where the first column is always the same. I want to collect all those files, extract the second columns by file wise and write the first column, followed by the other columns(extracted from files) next to each other. Any tricks , tips and hints. thanks K __________________________________ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail

3 5

How does import work?
by Johan Nilsson Feb. 1, 2005

Feb. 1, 2005

Hi all, I am rather new to python. I am trying to write a program using the scipy package. I have come across a problem that confuses me, and I hope that someone could give me an hint on how to solve this. Here is what I do Start idle >>> from scipy.signal.signaltools import * /Traceback (most recent call last): File "<pyshell#0>", line 1, in -toplevel- from scipy.signal.signaltools import * ImportError: No module named signaltools/ So I try the methodic way and this works, giving me access to the functions I need >>> from scipy import * >>> from scipy.signal import * >>> from scipy.signal.signaltools import * Now what confuses me is that when I put the above three lines in a file (of course without the >>>) and execute them I get a long error message. / Traceback (most recent call last): File "/home/johan/pyton/import_test.py", line 5, in -toplevel- from scipy.signal import * File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 270, in __getattr__ module = self._ppimport_importer() File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 233, in _ppimport_importer raise PPImportError,\ PPImportError: Traceback (most recent call last): File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 243, in _ppimport_importer module = __import__(name,None,None,['*']) File "/usr/lib/python2.3/site-packages/scipy/signal/__init__.py", line 11, in ? File "/usr/lib/python2.3/site-packages/scipy/signal/ltisys.py", line 14, in ? File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 270, in __getattr__ module = self._ppimport_importer() File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 233, in _ppimport_importer raise PPImportError,\ PPImportError: Traceback (most recent call last): File "/usr/local/lib/python2.3/site-packages/scipy_base/ppimport.py", line 243, in _ppimport_importer module = __import__(name,None,None,['*']) File "/usr/lib/python2.3/site-packages/Numeric/Matrix.py", line 5, in ? import LinearAlgebra File "/usr/local/lib/python2.3/site-packages/Numeric/LinearAlgebra.py", line 8, in ? import lapack_lite ImportError: /usr/local/lib/python2.3/site-packages/Numeric/lapack_lite.so: undefined symbol: dgesdd_/ What I dont understand is how can the import statements work, when I type them in manually in IDLE and not when I execute them in a file? Has anyone come across this type of behavior before? Johan

2 1

Traffic Network simulator
by Shitiz Bansal Feb. 1, 2005

Feb. 1, 2005

Hi, I need a traffic network simulator(for roads) for my project work.I would prefer the simulator to be in python so that i can reprogram/modify it according to my needs. does anyone know where i can find something of the sort or are there any special modules available which can help me build one? Shitiz __________________________________ Do you Yahoo!? All your favorites on one personal page � Try My Yahoo! http://my.yahoo.com

4 3

carriage return on windows
by Bill Kranec Feb. 1, 2005

Feb. 1, 2005

Hello, I'm trying to have a loop in a program print a message so I know it's status. Right now I'm using print "Percent completed:" + str(percent) + "\r" Which should send me back to the beginning of the line and overwrite it with a new line. But instead I get: Percent completed: 50 Percent completed: 51 Percent completed: 52 Percent completed: 53 and so on. Am I using this wrong, and if so, what is the right way to implement something like this? Thanks for any help! Bill

9 13

Comparing files, Counting Value
by Michiyo LaBerge Feb. 1, 2005

Feb. 1, 2005

Hello all, I'm very new to Python and have been trying to write a script to compare data from 2 files and getting a total. One of the two files contains x, y positions of pixels and a color value(z) of each, so it has three columns in the file. The other file has two columns; x1, y1. I'd like to get only x, y positions which match to x1, y1 of the second file and then look up the z value. If the z value is greater than a certain number, it counts 1, otherwise it moves on the next x, y position. Finally, I'm able to get total count of the pixels that are over the threshold. The script I'm using is below step by step, however, I haven't been able to figure out the error massage "IndexError: list index out of range" on z value. Any comments would be appreciated! Regards, Michiyo file 1: file 2: 299 189 8.543e-02 260 168 300 189 0.000e+00 270 180 301 189 0.000e+00 299 189 302 189 0.000e+00 300 170 0 188 5.095e-02 301 189 1 188 5.108e-02 . . . . . . . . . . . . #!usr/local/bin/python import sys i=open("file 1") #value data o=open("file 2") #look-up file l=open("result", 'w')#result results={} line=i.readline() line=o.readline() while line: fields=line.split() x1=fields[0, 1] in i #x,y position in file 1 z=fields[2] in i #value data in file 1 x2=fields[0, 1] in o #x,y position in file 2 if x1 == x2: read(z) if z >= 5.000e-02: z=1 count(n=0) print>>l, count(1) i.close() o.close() l.close()

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