🌐 Mailman 3 January 2008 - Python-list - python.org

Sine wave?
by EC Nov. 25, 2013

Nov. 25, 2013

Ive been banging my head against the wall for the past few days trying to generate a sine wave... My math skills arent the best, I'll admit, and I think I'm going crosseyed trying to understand this... I *think* the following code should work but it outputs some really weird stuff. I'm sorta new so please help if you can! Thank you Eric #------------------------------------------- import math import wave import string pi = math.pi sin = math.sin cos = math.cos #init output and related vars sr = 44100 Outfile = wave.open("outfile.wav", "w") Outfile.setnchannels(1) Outfile.setsampwidth(4) Outfile.setframerate(sr) Outfile.setcomptype("NONE", "Uncompressed") Outtemp = [] Outstr = "" def get_phase(curphs, freq): phinc = (freq*1.0000/sr*1.0000)*360 phase = curphs + phinc if phase >= 360: phase -= 360 elif phase < 0: phase += 360 return phase def gen_wav(sec, freq, ampcent): numsamp = sec*sr amp = (ampcent*1.0000/100)*32767 i = 0 temp = [] t = 0 curphase = 0 while i < numsamp: curphase = get_phase(curphase, freq) t = int(round(amp*sin(2*pi*curphase))) temp.append(t) i+=1 return temp Outtemp = gen_wav(.01, 440, 75) Outstr = string.join(map(str, Outtemp), ",") print Outstr Outfile.writeframes(Outstr) Outfile.close()

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Re: Proposal: [... for ... while cond(x)]
by Eighty Sept. 26, 2013

Sept. 26, 2013

Terry Reedy wrote: > whereas the analogous expansion of your proposal > > for x in xs: > while cond(x): > yield e(x) > > is an infinite loop and not at all what you mean. You're right. The syntax is ambiguous. I agree it's not a good idea, now. :) > x for x in xs while cond(x) if blah(x) > x for x in xs if blah(x) while cond(x) > x*y for x in xs while cond(x) for y in ys These wouldn't be a problem. "... for x in xs while cond(x) ..." would be transformed into "... for x in takewhile(cond, xs) ..." which could be applied to an if thingy if you first transform "... for x in xs if cond(x) ..." into "... for x in filter(cond, xs) ...".

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mutlifile inheritance problem
by maurelius01＠hotmail.com Sept. 21, 2013

Sept. 21, 2013

I have classes defined in different files and would like to inherit from a class in file A.py for a class in file B.py but am running into problems. I'm using Python 1.5.2 on Windows NT Here's a specific example: ************************ file cbase01.py: class CBase: def __init__(self): self.cclass = None print "cbase" class CImStream(CBase): def __init(self): CBase.__init__(self) print "CImStream" ************************* in file wrappers_A01.py: import cbase01 reload(cbase01) class ImStream_SavedBitmaps(cbase01.CImStream): def __init__(self): cbase.CImStream.__init__(self) print "SavedBitmaps" ************************** in file sequencer01.py import cbase01 # the offending lines, program works reload(cbase01) # if I comment these out. class Sequencer: def Append(self, item): pass ***************************** in test02.py import wrappers_A01 reload(wrappers_A01) import sequencer01 reload(sequencer01) x0 = wrappers_A01.ImStream_SavedBitmaps() *************************************************************** If I run test02 I get the traceback Traceback (innermost last): File "<string>", line 1, in ? File "D:\PythonCode\pna\eyeTracking\tests\test02.py", line 15, in ? x0 = wrappers_A01.ImStream_SavedBitmaps() File "D:\PythonCode\pna\eyeTracking\tests\wrappers_A01.py", line 21, in __init__ cbase.CImStream.__init__(self) TypeError: unbound method must be called with class instance 1st argument Any ideas what I am doing wrong? Thanks, Marc

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can't find win32api from embedded pyrun call
by Jim Sept. 6, 2013

Sept. 6, 2013

I am trying to figure out how to embed Python in a little C++ Windows console app. Here's the code: // Py_Initialize(); Py_InitializeEx(0); PyRun_SimpleString("from win32com.client import *"); Here's what it does on the last line: File "D:\Python\Lib\site-packages\win32com\__init__.py", line 5, in ? import win32api, sys, ok ImportError: No module named win32api The same line runs fine in IDLE or at the command prompt. It also runs without complaint if I run a release version of the app. To build the debug version I had to build python42_d.lib/dll myself. The reason I can't call PyInitialize is that it crashes with an "invalid signal" error. I don't think it's a path issue -- I've checked system path, sys.path, pythonpath env var, and the pythonpath entry in the registry, all of them loaded with directories including the one with win32api.pyd. Besides, if it were an install or path problem, why would it work at the command prompt? Could it be a problem with the debug lib I built? Any suggestions are welcome. -- Jim

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Best Python book(s) for a pre-teen?
by snarflemike＠yahoo.com Aug. 1, 2013

Aug. 1, 2013

Hi all, My son is 11 and wants to try programming, partly because it's what I do for a living. Even though I don't (yet?) use or even know Python, through some unexplainable thought process I've decided it would be a good language to start him off with. I've downloaded 2.2.2 and played around with it for a bit, and I would now like to hand him a book (with my guidance as needed) and say "go have fun!" Is there a book that would be suitable for this approach (again, assuming I'm around to help out as needed)? One other question -- I'd like him to be able to do simple graphics fairly early, since I think it makes the whole self-learning process much more interesting. I'm talking about things like points, lines, circles, fills, etc. Is there a binding to the Win32 graphics primatives in 2.2.2, or can I find one someplace? If this is a RTFM question, any pointers to TFM chapter, etc would be appreciated! Thanks for any guidance. I'm sure I'll end up having at least as much fun as he does. Mike

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how to get next month string?
by Yinghe Chen May 2, 2013

May 2, 2013

Hi, Could someone help on how to use python to output the next month string like this? "AUG07", suppose now is July 2007. I think also need to consider Dec 07 case, it is supposed to output as below: "JAN07". datetime module seems not supporting the arithmatic operations, any hints? Thanks in advance, Yinghe Chen

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Calling J from Python
by Gosi March 9, 2013

March 9, 2013

It is quite easy to call J from Python http://groups.google.com/group/J-Programming/browse_thread/thread/5e84b7566…

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Weirdness with python and stdin redirection under Win32
by Jonathan M. Gilligan Jan. 18, 2013

Jan. 18, 2013

I am getting an error reading stdin only when I invoke a python script by typing "bar | foo.py" or "foo.py < bar", but not when typing "bar | python foo.py" or "python foo.py < bar". The error arises ecause when input is redirected, stdin has fileno = -1 if the script is invoked as "foo.py", but correctly has fileno = 0 if it is invoked as "python foo.py" Consider the following script, which I want to use as a prototype for a simple stdin --> stdout filter: # foo.py import sys print "fileno = ", sys.stdin.fileno() lines = sys.stdin.xreadlines() for line in lines: sys.stdout.write(line) On win32 (Win2k pro, SP3), using ActiveState ActivePython 2.2.1 build 222, I can execute foo.py either by typing "foo.py" or "python foo.py" on the command line (the relevant registry key for opening .py files has command 'C:\Python22\python.exe "%1" %*'). If I type "echo bar | foo.py", I get C:\>echo bar | foo.py The process tried to write to a nonexistent pipe. fileno = -1 Traceback (most recent call last): File "C:\foo.py", line 7, in ? lines = sys.stdin.readlines() IOError: [Errno 9] Bad file descriptor whereas if I type "echo bar | python foo.py", I get C:\>echo bar | python foo.py fileno = 0 bar Other tests yield: C:\>foo.py < foo.py fileno = -1 Traceback (most recent call last): File "C:\Documents and Settings\Jonathan\My Documents\Programming\Omap VU\Fast CameraDriver\BF_LabView\Leo\foo.py", line 7, in ? for line in lines: IOError: [Errno 9] Bad file descriptor C:\>python foo.py < foo.py fileno = 0 # foo.py import sys print "fileno = ", sys.stdin.fileno() lines = sys.stdin.xreadlines() for line in lines: sys.stdout.write(line) If I just type "foo.py" or "python foo.py" on the command line, I get "fileno = 0" in both cases and the script works identically in both cases. Can anyone explain what's happening? Why the file descriptor for redirected stdin has a fileno of -1 if the python script is invoked using "foo.py" but not when it's invoked with "python foo.py"? Thanks, Jonathan

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PHP vs. Python
by stephen.mayer＠gmail.com Sept. 25, 2012

Sept. 25, 2012

Anyone know which is faster? I'm a PHP programmer but considering getting into Python ... did searches on Google but didn't turn much up on this. Thanks! Stephen

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Re: Storing of folder structure in SQL DB
by Sergei Minayev Sept. 21, 2012

Sept. 21, 2012

Amit Khemka: > On 5 Apr 2007 04:58:22 -0700, Sergei Minayev <sergei.minayev(a)gmail.com> wrote: > > Hi All! > > Can you please help me with the following problem: > > I need to store a copy of local folders structure in MySQL database. > > I have chosen the following table structure for that: > > ------------------------------------------------ > > | id | id_uplink | folder_name | > > ------------------------------------------------ > > id - unique property of each folder. > > id_uplink - id of upper level folder is stored here (for example: if > > id of c:\test is 1, than id_uplink of c:\test\python equals 1). > > folder_name - name of folder. > > You see, i dont want to store the path list, but the structure. > > > > The question is how to implement that in Python. I easily made it in C+ > > + using recursion. But, unfortunately, I can't figure it out how to > > make it in python using os.walk function (or can you recommend smth. > > else???). :( Though it looks quite simple, but anyway. > > > > Best Regards, > > os.walk should be more than sufficient in your case. You can navigate > the directory structure and at each 'new' directory find its parents > id and assign a new-id to this 'new' directory. > > An Example: > > import os > root='/my/root/directory' > id =0 > tree={root:(-1, id)} > id+=1 > for path, dirs, files in os.walk(root): > for dir in dirs: > if not tree.has_key(path+'/'+dir): > tree[path+'/'+dir]=(tree[path][1], id) > id+=1 > > It stores ids as a tuple (parent_id, id) in a dictionary(tree). Should > be straight forward to modify to your requirements. Also you can make > the following code more efficient by saving/caching some lookups ! > > Cheers, > -- > ---- > Amit Khemka -- onyomo.com > Home Page: www.cse.iitd.ernet.in/~csd00377 > Endless the world's turn, endless the sun's Spinning, Endless the quest; > I turn again, back to my own beginning, And here, find rest. Thanks! Your code example was really helpful!

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