Re: [Tutor] Bitmap editor and File-saving
Johnston Jiaa [EMAIL PROTECTED] wrote I am using Tkinter to create a program in which the user can draw a simple bitmap image. What library would be best to use in this circumstance? I have no idea how I would go about doing this except maybe I would use Tkinter's canvas component? The canvas widget is probably adequate for simple drawing. More advanvced libraries like PIL might be useful for converting the format or doing large scale transformations. In order for the program to be useful, it should save the picture too. I'd like for it to save the image with some strings of text. How can I implement such a file-saving feature? You could either save two files one with the text and the other the bitmap. Or you could convert the text to binary data and write it to the same file as the bitmap. To read it back you will need to write code to strip the text off again however. Or you could use uuencode, or similar, to convert the image to text and add your strings to that. Again you will need to write the reverse process for retrieving it. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Wrong version of Python being executed
Martin Walsh mwalsh at groktech.org Sun Nov 11 06:13:10 CET 2007 That is odd. Try using the full path to python, just to be sure: c:\python25\python script.py -- do you get the same behavior? This works just fine- I would expect it to. Also, if you haven't already, you can run python with the -E and/or -S flags (ex. 'c:\python25\python -E -S script.py'). The -E flag will cause the PYTHONPATH and PYTHONHOME environment variables to be ignored. And This also works just fine. I've tried both switches independently, and the scrip runs normally when I use either and both at the same time. If I don't use them, then Python2.3 is being invoked somehow. However, when I type set PYTHONPATH and set PYTHONHOME at the cmd prompt SET PYTHONPATH Environment variable PYTHONPATH not defined SET PYTHONHOME Environment variable PYTHONHOME not defined Very strange indeed. It's starting to remind me of an episode from The Twilight Zone ;-) Is ti possible that my registry is corrupted? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Wrong version of Python being executed
Tony Cappellini wrote: Martin Walsh mwalsh at groktech.org Sun Nov 11 06:13:10 CET 2007 That is odd. Try using the full path to python, just to be sure: c:\python25\python script.py -- do you get the same behavior? This works just fine- I would expect it to. Actually, I would have expected the opposite. My initial thought based on your description was that python2.5 is being invoked with PYTHON* env vars from a previous install, or some site module weirdness. But, the fact that running python.exe with it's full path corrects the issue, seems to indicate a problem with your PATH, rather than any python specific environment setting. What does 'set PATH' report? Though this still doesn't explain why you get python2.5 interactively, and python2.3 when running a script -- perhaps I'm still unclear what you are seeing. Would the following be an accurate description of the behavior? assuming: - you run inside a fresh 'cmd' console each time (typing 'cmd' at the run dialog, or similar), to be sure there is no app environment kruft - the current working directory doesn't contain any programs, scripts or possibly links that could interfere (preferably an empty path) - you don't have any PYTHON* environment vars set (including PYTHONSTARTUP) you observe: - when you type 'python' (only 'python') at the prompt, you get python2.5 interactively - when you use the form 'python script.py', the script is run with python2.3 (can you verify with sys.version?) with sys.path appropriate for 2.3 - when you use the form 'c:\python25\python.exe script.py', the script is executed with python2.5 and you have the correct sys.path (for 2.5) Also, if you haven't already, you can run python with the -E and/or -S flags (ex. 'c:\python25\python -E -S script.py'). The -E flag will cause the PYTHONPATH and PYTHONHOME environment variables to be ignored. And This also works just fine. I've tried both switches independently, and the scrip runs normally when I use either and both at the same time. If I don't use them, then Python2.3 is being invoked somehow. Yeah, very odd indeed. Very strange indeed. It's starting to remind me of an episode from The Twilight Zone ;-) Is ti possible that my registry is corrupted? I wouldn't think so, but I suppose it is possible. I believe all the pertinent registry keys are store under HKLM\Software\Python\Pythoncore\version, so you could have a look. There are settings stored elsewhere, but I think they are all related to file associations, and enabling double-click launching etc. I hope someone will correct or clarify, if I'm wrong. If it is a registry issue, re-installing python2.5 *may* provide a quick fix. BTW, are you using an alternate distribution of python (ex. ActiveState), or the standard python.org version? HTH, Marty ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Problem with default arguments for function
I just discovered mpmath (http://code.google.com/p/mpmath/wiki/Documentation) and am trying to write a useful function that uses it to compute factorials. Here's what I have: def fact(n, precision=15, full=False): compute n! from mpmath import mpf if not isinstance(n, int): return None elif n 0: return None n = mpf(n) if full: precision = n * 10 # ensures that for n 1 billion, product will not be in scientific notation (i.e., no '+') mpf.dps = precision product = mpf(1) while n mpf(1): product *= n n -= 1 if '+' in str(product): return product else: return int(str(product)[:-2]) # product is a float, ending in '.0', so this needs to be removed and string converted to int. The code is also at http://python.pastebin.com/m33d52d54. And a couple of example uses that illustrate my problem: # 1 (precision default overridden and set to 20; full left at default of False) print fact(50, 20) 3.0414093201713378044e+64 # 2 (both precision and full left at their defaults) print fact(50) 3.04140932017134e+64 # 3 (full set to True, forcing precision to be specified--but irrelevant what it is set to) print fact(50, 3, True) 30414093201713378043612608166064768844377641568960512 # 4 (see # 3) print fact(50, 30, True) 30414093201713378043612608166064768844377641568960512 And if the function is rewritten as def fact(n, full=False, precision=15) there would be the analogous problem involving full. Is there a way to solve this problem of the unnecessary setting of the 2nd argument? Thanks, Dick Moores ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Problem with default arguments for function
Dick Moores [EMAIL PROTECTED] wrote And if the function is rewritten as def fact(n, full=False, precision=15) there would be the analogous problem involving full. Is there a way to solve this problem of the unnecessary setting of the 2nd argument? The most common solution I've seen is to write wrappers around the basic function like: def fullFact(n, precision=15): return fact(n,True,precision) def precisionFact(n, full=False): return fact(n, full, 15) Not terribly elegant but is at least short and simple. -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Wrong version of Python being executed
Martin Walsh [EMAIL PROTECTED] wrote Try using the full path to python, just to be sure: c:\python25\python script.py -- do you get the same behavior? This works just fine- I would expect it to. Actually, I would have expected the opposite. Me too. Though this still doesn't explain why you get python2.5 interactively, and python2.3 when running a script -- perhaps I'm still unclear what you are seeing. Would the following be an accurate description of the behavior? assuming: - you run inside a fresh 'cmd' console each time (typing 'cmd' at the run dialog, or similar), to be sure there is no app environment kruft This is very important. If you just type python at the Run dialog it uses a different algorithm to find the exe than if you type python at a DOS prompt inside a CMD window. Its the second algorithm that is used if you type python foo.py at a cmd prompt but the first that is used if you double click foo.py within explorer (actually that could even be a different one again!) or type python foo.py in the Run dialog. fix. BTW, are you using an alternate distribution of python (ex. ActiveState), or the standard python.org version? That *shouldn't* make any difference...but you can never be 100% sure! -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] manipulating data
Using,
fields = {}
for line in open('data.txt') :
if line :
if line.split()[0] == 'field' :
field = int(line.split()[-1])
else :
fields[field] = tuple(line.split())
I get,
fields[field] = tuple(line.split())
NameError: name 'field' is not defined
On Nov 8, 2007 7:34 AM, Ricardo Aráoz [EMAIL PROTECTED] wrote:
Kent Johnson wrote:
Bryan Fodness wrote:
I would like to have my data in a format so that I can create a contour
plot.
My data is in a file with a format, where there may be multiple fields
field = 1
1a 0
If your data is really this regular, it is pretty easy to parse. A
useful technique is to access a file's next method directly. Something
like this (not tested!):
f = open('data.txt')
fields = {} # build a dict of fields
try:
while True:
# Get the field line
line = f.next()
field = int(line.split()[-1]) # last part of the line as an int
f.next() # skip blank line
data = {} # for each field, map (row, col) to value
for i in range(20): # read 20 data lines
line = f.next()
ix, value = f.split()
row = int(ix[:-1])
col = ix[-1]
data[row, col] = int(value)
fields[field] = data
f.next()
except StopIteration:
pass
Or maybe just (untested) :
fields = {} # build a dict of fields
for line in open('data.txt') :
if line :# skip blank lines
if line.split()[0] == 'field' :
field = int(line.split()[-1])
else :
fields[field] = tuple(line.split())
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Re: [Tutor] Problem with default arguments for function
Dick Moores wrote: def fact(n, precision=15, full=False): ... # 3 (full set to True, forcing precision to be specified--but irrelevant what it is set to) print fact(50, 3, True) 30414093201713378043612608166064768844377641568960512 You don't have to specify precision if you pass full as a keyword argument: fact(50, full=True) Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Problem with default arguments for function
At 04:22 PM 11/11/2007, Alan Gauld wrote: Dick Moores [EMAIL PROTECTED] wrote And if the function is rewritten as def fact(n, full=False, precision=15) there would be the analogous problem involving full. Is there a way to solve this problem of the unnecessary setting of the 2nd argument? The most common solution I've seen is to write wrappers around the basic function like: def fullFact(n, precision=15): return fact(n,True,precision) def precisionFact(n, full=False): return fact(n, full, 15) Not terribly elegant but is at least short and simple. Alan, I won't adopt this solution for my fact(), but I'm glad to know about it. Thanks, Dick ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Problem with default arguments for function
At 05:38 PM 11/11/2007, Kent Johnson wrote: Dick Moores wrote: def fact(n, precision=15, full=False): ... # 3 (full set to True, forcing precision to be specified--but irrelevant what it is set to) print fact(50, 3, True) 30414093201713378043612608166064768844377641568960512 You don't have to specify precision if you pass full as a keyword argument: fact(50, full=True) Ah, good to know. Thanks. Dick ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Problem with default arguments for function
At 05:10 PM 11/11/2007, Michael H. Goldwasser wrote: Dick, Another typical strategy is to use some prescribed special value for the precision parameter to designate the desire for full precision. For example, since precisions should presumably be positive, one could design this function as: def fact(n, precision=15): compute n!. precisionthe minimum desired precision. If -1 is specified, computed to full precision. # ... if precision == -1: precision = n * 10 # insures that for n 1 billion, ... # ... If you are not happy with the oddity of -1 (or in cases where -1 might be a legitimate parameter value), you can pick the flag from a different data type. In this case, perhaps None would be a more natural way to say that you do not want any limit on the precision. So this could be coded as def fact(n, precision=15): compute n!. precisionthe minimum desired precision. If None is specified, computed to full precision. # ... if precision is None: precision = n * 10 # insures that for n 1 billion, ... # ... Looking at your examples, this should (unteste) behave as: # 1 (precision default overridden and set to 20) print fact(50, 20) 3.0414093201713378044e+64 # 2 (without explicit value, precision defaults to 15) print fact(50) 3.04140932017134e+64 # 3 (explicitly says not to limit precision) print fact(50, None) 30414093201713378043612608166064768844377641568960512 Beautiful! Thanks! Dick ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Problem with default arguments for function
Dick, Another typical strategy is to use some prescribed special value for the precision parameter to designate the desire for full precision. For example, since precisions should presumably be positive, one could design this function as: def fact(n, precision=15): compute n!. precisionthe minimum desired precision. If -1 is specified, computed to full precision. # ... if precision == -1: precision = n * 10 # insures that for n 1 billion, ... # ... If you are not happy with the oddity of -1 (or in cases where -1 might be a legitimate parameter value), you can pick the flag from a different data type. In this case, perhaps None would be a more natural way to say that you do not want any limit on the precision. So this could be coded as def fact(n, precision=15): compute n!. precisionthe minimum desired precision. If None is specified, computed to full precision. # ... if precision is None: precision = n * 10 # insures that for n 1 billion, ... # ... Looking at your examples, this should (unteste) behave as: # 1 (precision default overridden and set to 20) print fact(50, 20) 3.0414093201713378044e+64 # 2 (without explicit value, precision defaults to 15) print fact(50) 3.04140932017134e+64 # 3 (explicitly says not to limit precision) print fact(50, None) 30414093201713378043612608166064768844377641568960512 With regard, Michael On Sunday November 11, 2007, Dick Moores wrote: def fact(n, precision=15, full=False): compute n! And a couple of example uses that illustrate my problem: # 1 (precision default overridden and set to 20; full left at default of False) print fact(50, 20) 3.0414093201713378044e+64 # 2 (both precision and full left at their defaults) print fact(50) 3.04140932017134e+64 # 3 (full set to True, forcing precision to be specified--but irrelevant what it is set to) print fact(50, 3, True) 30414093201713378043612608166064768844377641568960512 # 4 (see # 3) print fact(50, 30, True) 30414093201713378043612608166064768844377641568960512 And if the function is rewritten as def fact(n, full=False, precision=15) there would be the analogous problem involving full. Is there a way to solve this problem of the unnecessary setting of the 2nd argument? Thanks, Dick Moores ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] [tutor] File format conversion
Hello All, In one application i want to convert format of ascii file to binary file. And using that binary file in a function of PIL i can convert it to an image file. So i wanted to know how to convert the file format in python... is it possible by Numpy ?? And is there any other alternative to convert an ascii into an bitmap image directly in PIL without Numpy?? thanks, -- Varsha ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] assignment question
Hello, Why does the following not return [1,2,3,4] ? x = [1,2,3].append(4) print x None ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] assignment question
On 12/11/2007, Ryan Hughes [EMAIL PROTECTED] wrote: Why does the following not return [1,2,3,4] ? x = [1,2,3].append(4) print x None List methods like .append() and .sort() modify lists in-place, as opposed to creating new lists. To remind you of this, those methods return None instead of returning the modified list. Otherwise (if .append() returned the modified list), you might be tempted to write code like this: x = getSomeList() y = x.append(3) and forget that x and y are the same list. If you want to join two lists together to make a new one, you can use +: x = [1, 2, 3] + [4] x [1, 2, 3, 4] Hope this helps, -- John. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Tutor Digest, Vol 45, Issue 30
Message: 4 Date: Mon, 12 Nov 2007 00:16:35 - From: Alan Gauld [EMAIL PROTECTED] Subject: Re: [Tutor] Wrong version of Python being executed To: tutor@python.org Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; format=flowed; charset=iso-8859-1; reply-type=original This is very important. If you just type python at the Run dialog it uses a different algorithm to find the exe than if you type python at a DOS prompt inside a CMD window. I never type anything in the Run dialog other than Regedit, or CMD. I dont want that to sound defensive, but usually when I need a CMD prompt, I'm need to be there for a long time, and that's why I open it. It never even occurred to me to type Python at the Run prompt. Most of the time, I open a cmd prompt IN the directory where I want to run a script, by using Command Prompt Here, from Microsoft. (why isn't this built into the OS after all this time ??) But while troubleshooting this problem, I've not been using it, and have been CD'ing down to where my sources are. Its the second algorithm that is used if you type python foo.py at a cmd prompt but the first that is used if you double click foo.py within explorer I typically dont double click my scripts, unless they are guis, or exes' That *shouldn't* make any difference...but you can never be 100% sure! I think a this point, I'll just re-install 2.3 and 2.5 to see if that fixes it, with a reboot in-between. I dont know what else to do. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] assignment question
On Sunday November 11, 2007, Ryan Hughes wrote: Hello, Why does the following not return [1,2,3,4] ? x = [1,2,3].append(4) print x None The reason is that the append method does not return anything. In effect, the expresison [1,2,3].append(4) temporarily causes 4 to be appended to the (unnamed) list. However the assignment x = blah sets the variable x equal to the result of the expression blah (which in this case is None, since append does not return anything). In contrast, consider the following interaction: x = [1,2,3] x.append(4) print x [1, 2, 3, 4] ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Wrong version of Python being executed
Message: 2 Date: Sun, 11 Nov 2007 16:57:01 -0600 From: Martin Walsh [EMAIL PROTECTED] Subject: Re: [Tutor] Wrong version of Python being executed To: Tutor Python tutor@python.org Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1 My initial thought based on your description was that python2.5 is being invoked with PYTHON* env vars from a previous install, or some site module weirdness. Not sure how the previous install surfaced, but I installed all python installations and packages on my computer. I have to switch between 2.3 and 2.5, so to make it easy, I use an environment variable called CURRENT_PYTHON. (someone on this list or the wxPython list told me I should NOT use PYTHONPATH and modify it the way I am using CURRENT_PYTHON) CURRENT_PYTHON=C:\PYTHON2X path=%CURRENT_PYTHON% (The existing path isn't shown, only for brevity) Note, these are entered in Ctrl Panel, System environment variables, NOT at the command line. But, the fact that running python.exe with it's full path corrects the issue, seems to indicate a problem with your PATH, rather than any python Yes, my conclusion also, but what is wrong with the path? I've posted the contents of PATH in the original email or one of the subsequent ones. Would the following be an accurate description of the behavior? assuming: - you run inside a fresh 'cmd' console each time (typing 'cmd' at the run dialog, or similar), to be sure there is no app environment kruft correct- - the current working directory doesn't contain any programs, scripts or possibly links that could interfere (preferably an empty path) Not that I can see - you don't have any PYTHON* environment vars set (including PYTHONSTARTUP) No- see for yourself. No python anything variables. C:\Documents and Settings\z30032asset python Environment variable python not defined you observe: - when you type 'python' (only 'python') at the prompt, you get python2.5 interactively Correct - when you use the form 'python script.py', the script is run with python2.3 (can you verify with sys.version?) with sys.path appropriate for 2.3 Correct - when you use the form 'c:\python25\python.exe script.py', the script is executed with python2.5 and you have the correct sys.path (for 2.5) Correct I wouldn't think so, but I suppose it is possible. I believe all the pertinent registry keys are store under HKLM\Software\Python\Pythoncore\version, so you could have a look. Already did. There IS a PYTHONPATH entry for each of the 3 versions of Python I have installed. They are all identical, with the exception of the last 2 digits for the Python version. This looks ok to me. No other rogue entries of PYTHONPATH were found in the registry. BTW, are you using an alternate distribution of python (ex. ActiveState), or the standard python.org version? No. I always use the regular Python.Org distributions. I never understood what was so special about ActiveState anyway. I;d rather have full control of my installs, and all the packages. Although, at this point, I'm not in control over what is happening with my path ;-) ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] assignment question
Ryan Hughes wrote: Hello, Why does the following not return [1,2,3,4] ? x = [1,2,3].append(4) print x None because the append() method doesn't return a copy of the list object; it just modifies the list itself. so your code constructs a list object with 3 elements, appends a fourth element to it, and throws that list object away, keeping only the return value of append(). ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] assignment question
Append modifies the array as a side effect. It has no meaningful return value. x = [1, 2, 3] x.append(4) print x [1, 2, 3, 4] - Jeff Younker - [EMAIL PROTECTED] - 510.798.5804 - On Nov 11, 2007, at 8:21 PM, Ryan Hughes wrote: Hello, Why does the following not return [1,2,3,4] ? x = [1,2,3].append(4) print x None ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Swapping variables ...
On 11/10/07, O.R.Senthil Kumaran [EMAIL PROTECTED] wrote: After quizzing newbies in C on swapping without 3rd variable, I found this to be really *cool* construct to swap :) x = 10 y = 20 x,y = y,x Keep in mind that, this is actually a tuple assignment. A new tuple x,y is created with the older one y,x, and with the side effect thatthe variables are swapped as we see it. you can dig even *deeper* within the tuple assignment. keep in mind that the right-hand side (RHS) is always evaluated 1st, whenever there is an assignment operation. an alias or reference mapping is made using the variable name (in the current or designated namespace) to whatever object appears on the RHS. this means that 'x' on the LHS gets whatever object 'y' was referencing during evaluation time, and likewise, 'y' becomes an alias to whatever object 'x' was pointing to. it's just a coincidence that the new mapping variables are just reversed to what they were previously. the interpreter makes no special distinction just because this is the case. if you are still thinking of variables as data structures which contain values, you need to unlearn what you have learned. :-) variables in Python are merely references to objects and such references can be manipulated at will. for example, a variable 'a' as in 'a = 123' can be immediately reassigned to a string, i.e., a = 'foo'. getting comfortable with objects, references, and the mapping of names to objects are some ways of understanding Python more fully and with greater success. hope this helps! -- wesley - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Core Python Programming, Prentice Hall, (c)2007,2001 http://corepython.com wesley.j.chun :: wescpy-at-gmail.com python training and technical consulting cyberweb.consulting : silicon valley, ca http://cyberwebconsulting.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
