Re: [Tutor] need help with syntax
On Tue, 10 Jan 2006, bill nieuwendorp wrote:
I am trying to convert binary file to ascii
here is the format spec
steps = int 4
value = int 4
time = float 4 * steps
Hi Bill,
Ok, that structure seems fairly simple so far.
import struct
import string
f = file('binary_file','rb')
line = f.readline()
Ah. Don't do this. *grin*
If our file is binary, the only safe function we can use to read from such
a file is read(). newlines() just shouldn't be a concept in binary
files: using readline() on a binary file is a major no-no.
Imagine what happens if your file only contains ten steps. As a hint:
look at ord('\n').
You mentioned earlier that you're expecting an integer, an integer, and
then a sequence of float. Don't count bytes if you can help it: let
Python's struct.calcsize() do this for you.
http://www.python.org/doc/lib/module-struct.html
Your machine may align bytes differently than you might expect: it may be
best to let the machine handle that for you.
Best of wishes to you!
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Re: [Tutor] How can I make a python script go directory by directory and excecute on files of choice
On 11/01/06, Liam Clarke [EMAIL PROTECTED] wrote: Hi Srinivas - For walking a directory, you can use os.walk() or os.path.walk(), but I prefer the path module here - http://www.jorendorff.com/articles/python/path/. The Path module is excellent, but it's walk still doesn't take into account the depth of the current file in the folder structure. If you need that, I wrote (with Kent's help) a simple script that will take it into account (you need the Path module above for it to work). def traverse(directory, function, depth=0): import path thedir = path.path(directory) for item in thedir.files(): function(item, depth) for item in thedir.dirs(): traverse(item,function, depth+1) It can be used like: def doprint(item, depth): print item traverse(rC:\Temp, doprint) Hope it's helpful to someone. Ed ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] extra characters in XML
Hello all
I want to do the following in an XML file:
XFile = open(XmlFile,'r')
for line in XFile.readlines():
if line.find('end_time') 0:
print line
However, it does not work due to extra characters that
appear in the XML file. For example if I use the
previous code without the if condition, on a console
it looks like:
e n d _ t i m e
And if you output that to a text file and open that in
a text editor, the text editor shows a square instead
of a space in between every character. What is going
on?
Thanks
Ben
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[Tutor] pointers
Hi,
I f I want to translate C code to Python and have a function like
void get_args(int argc, char* argv[], Argument* args)
{
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Re: [Tutor] pointers
Sorry for the previous message I did it by mistake..the function was like below:
void get_args(int argc, char* argv[], Argument* args){ //check the amount of the arguments if(argc%2 == 0)
{ printf(Error, incorrect argument numbers : %d\n,argc); print_help(); exit(1); }
.
.
}
My first question about the pointers here; how can I convert them to Python?
And second and may be a little stupid; do I need to define argc how can I get arguments in python ?
Thanks in advance,
Burge
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Re: [Tutor] extra characters in XML
Found the following (which solved the problem, though
not on the console) at
http://www.jorendorff.com/articles/unicode/python.html
import codecs
# Open a UTF-8 file in read mode
infile = codecs.open(infile.txt, r, utf-8)
# Read its contents as one large Unicode string.
text = infile.read()
# Close the file.
infile.close()
The same function is used to open a file for writing;
just use w (write) or a (append) as the second
argument.
--- Ben Vinger [EMAIL PROTECTED] wrote:
Hello all
I want to do the following in an XML file:
XFile = open(XmlFile,'r')
for line in XFile.readlines():
if line.find('end_time') 0:
print line
However, it does not work due to extra characters
that
appear in the XML file. For example if I use the
previous code without the if condition, on a console
it looks like:
e n d _ t i m e
And if you output that to a text file and open that
in
a text editor, the text editor shows a square
instead
of a space in between every character. What is
going
on?
Thanks
Ben
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Re: [Tutor] extra characters in XML
Ben Vinger wrote:
Found the following (which solved the problem, though
not on the console) at
http://www.jorendorff.com/articles/unicode/python.html
import codecs
# Open a UTF-8 file in read mode
infile = codecs.open(infile.txt, r, utf-8)
# Read its contents as one large Unicode string.
text = infile.read()
# Close the file.
infile.close()
The same function is used to open a file for writing;
just use w (write) or a (append) as the second
argument.
Ben,
Most likely your XML file is 16-bit unicode, not utf-8. When ascii text
is represented as unicode, every other byte will be a null byte. That is
the extra character that shows up as a space or box depending on who is
interpreting it. The utf-8 codec must be swallowing the null bytes.
The first line of your XML should show what encoding it is if it is
different from utf-8. What is in that line?
In your code above, instead of utf-8 try utf_16_be and utf_16_le, one of
them should work.
Kent
--- Ben Vinger [EMAIL PROTECTED] wrote:
Hello all
I want to do the following in an XML file:
XFile = open(XmlFile,'r')
for line in XFile.readlines():
if line.find('end_time') 0:
print line
However, it does not work due to extra characters
that
appear in the XML file. For example if I use the
previous code without the if condition, on a console
it looks like:
e n d _ t i m e
And if you output that to a text file and open that
in
a text editor, the text editor shows a square
instead
of a space in between every character. What is
going
on?
Thanks
Ben
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Re: [Tutor] pointers
Hi Burge,
You can access command line argument via sys.argv:
import sys
print sys.argv
This prints a list of the command line arguments. Since argv is a
list, it means you can check its length to get the argument count:
print len( sys.argv )
There is always at least one argument in this list, if no argument was
supplied, then you get an empty string.
Hope this helps
Bernard
On 1/11/06, Burge Kurt [EMAIL PROTECTED] wrote:
Sorry for the previous message I did it by mistake..
the function was like below:
void get_args(int argc, char* argv[], Argument* args)
{
//check the amount of the arguments
if(argc%2 == 0)
{
printf(Error, incorrect argument numbers : %d\n,argc);
print_help();
exit(1);
}
.
.
}
My first question about the pointers here; how can I convert them to Python?
And second and may be a little stupid; do I need to define argc how can I
get arguments in python ?
Thanks in advance,
Burge
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Re: [Tutor] pointers
Burge Kurt wrote:
Sorry for the previous message I did it by mistake..
the function was like below:
void get_args(int argc, char* argv[], Argument* args)
{
//check the amount of the arguments
if(argc%2 == 0)
{
printf(Error, incorrect argument numbers : %d\n,argc);
print_help();
exit(1);
}
.
.
}
My first question about the pointers here; how can I convert them to
Python?
Python doesn't have pointers in the sense of direct references to
memory. Python has very good built in support for higher-level
structures than C has. Strings and lists are both built in.
As Bernard has pointed out, where a C function might have a count (argc)
and a pointer to an array of pointers to strings (char* argv[]), Python
uses just a list of strings.
I'll guess that Argument* args is a pointer to an array of Argument
objects. In Python this would be represented by a list of Argument objects.
Use of lists and strings should be covered in any introductory Python
tutorial or book; you might find one you like here:
http://wiki.python.org/moin/BeginnersGuide/NonProgrammers
http://wiki.python.org/moin/IntroductoryBooks
Kent
And second and may be a little stupid; do I need to define argc how can
I get arguments in python ?
Thanks in advance,
Burge
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[Tutor] CPU Utilization
I am implementing a computational cluster and am using a job controller (for want of a better term) that contacts the worker computers, determines how busy they currently are, and then assigns more work if the worker computer is below a certain cpu utilization threshhold. For the cpu threshhold, I've been thinking I'd have the worker computer shell out to perform the top command, parse the results, and report those values to the job controller. Is there a better way, or more pythonic, way to do this? Thanks ds ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pointers
On 1/11/06, Kent Johnson [EMAIL PROTECTED] wrote:
Burge Kurt wrote:
void get_args(int argc, char* argv[], Argument* args)
My first question about the pointers here; how can I convert them to
Python?
Python doesn't have pointers in the sense of direct references to
memory. Python has very good built in support for higher-level
structures than C has. Strings and lists are both built in.
the main reason why pointers are used in C (and C++) is so that the
called function has the ability to modify the object (since it is
passed by reference).
in Python, references to objects passed in are also live, meaning
that if it is a mutable (modifiable) object, you can manipulate it
directly without using the asterisk/star (*).
in bernard's example, we've replaced char* argv[] as an argument to
main by doing an import of sys and using the argv attribute of the sys
module, i.e., sys.argv. to access individual arguments, you would
replace something like:
for (int i = 0; i argc; i++) {
:
... argv[i] ...
:
}
... with ...
for i in range(len(sys.argv)):
:
... sys.argv[i] ...
:
... or ...
for eachArg in sys.argv:
:
... eachArg ...
:
I'll guess that Argument* args is a pointer to an array of Argument
objects. In Python this would be represented by a list of Argument objects.
it looks like it's a set of variable arguments (varargs). Python has
support for this too, and it's one of the rare places you will see
asterisks (*) used.
we replace void get_args(int argc, char* argv[], Argument* args)
with def get_args(*args). (recall that argv is sys.argv and argc is
len(sys.argv).) then to access each extra argument, you would:
for eachArg in args:
:
... eachArg ...
hope this helps!
-- wesley
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Core Python Programming, Prentice Hall, (c)2006,2001
http://corepython.com
wesley.j.chun :: wescpy-at-gmail.com
cyberweb.consulting : silicon valley, ca
http://cyberwebconsulting.com
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Re: [Tutor] pointers
On Wed, 11 Jan 2006, Burge Kurt wrote:
I f I want to translate C code to Python and have a function like
void get_args(int argc, char* argv[], Argument* args)
{
Hi Burge,
Also wanted to note that the Standard Library already contains an
argument-parsing library, so you may want to take advantage of it. The
library is called 'optparse':
http://python.org/doc/lib/module-optparse.html
It's something to keep in mind, just in case during your porting effort
you have the freedom to reuse the Standard Library.
Good luck!
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Re: [Tutor] CPU Utilization
Hi,
top is very interactive so it would not be easy at all to parse.
I can suggest reading /proc/loadavg if you're in Linux.
proc(5) ('man 5 proc') says that /proc/loadavg is
The load average numbers give the number of jobs in
the run queue averaged over 1, 5 and 15 minutes.
They are the same as the load average numbers given
by uptime(1) and other programs.
It can be easily parsed with split()
Hope that helps,
Hugo
DS wrote:
I am implementing a computational cluster and am using a job controller
(for want of a better term) that contacts the worker computers,
determines how busy they currently are, and then assigns more work if
the worker computer is below a certain cpu utilization threshhold.
For the cpu threshhold, I've been thinking I'd have the worker computer
shell out to perform the top command, parse the results, and report
those values to the job controller.
Is there a better way, or more pythonic, way to do this?
Thanks
ds
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Re: [Tutor] need help with syntax
You mentioned earlier that you're expecting an integer, an integer, and then a sequence of float. Don't count bytes if you can help it: let Python's struct.calcsize() do this for you. http://www.python.org/doc/lib/module-struct.html Your machine may align bytes differently than you might expect: it may be best to let the machine handle that for you. Erk, Danny, is of course, right. Perhaps I could rewrite my earlier suggestion as - stepValPattern = 2i bytesToRead = struct.calcsize(stepValPattern) bytes = f.read(bytesToRead) (steps, value) = struct.unpack(stepValPattern, bytes) floatPattern = %df % steps bytesToRead = struct.calcsize(floatPattern) bytes = f.read(bytesToRead) floatList = struct.unpack(floatPattern, bytes) f.read() works like following, (rough explanation follows) Let's say you have a 10 byte file - 00 0E A1 DC B3 09 FF AA B1 B2 00 f.read(3) will return 00 0E A1. Your file reference is now pointing at the 4th byte of the file, like so. 00 0E A1 DC B3 09 FF AA B1 B2 00 ...^ -current read position So calling f.read(3) again will return DC B3 09 Calling f.tell() will return the curernt read position, which would now be 6, the 7th byte (remembering computers count from 0 up.) f.seek(x) tells Python to move the read position to the xth byte of the file. You can use that with text files. I.E. If you've just called f.readlines(), you can use f.seek(0) to return to the start of the file. Anyway, I digress, but I'm trying to clarify how struct and f.read() work together. So, let's pretend all integers are 4 bytes, ditto all floats, and there's no byte alignment going on whatsoever. (of course, in real life you can't, hence using struct.calcsize()) So, you have a file like so - 03 00 00 00 0A 00 00 00 09 0B 21 CD That's step value step number of floats 03 00 00 00| 0A 00 00 00| 09 0B 21 CD ^ -- read pos stepValPattern = 2i bytesToRead = struct.calcsize(stepValPattern) #bytesToRead is 8 (idealised ints) bytes = f.read(bytesToRead) At this point, bytes is 03 00 00 00 0A 00 00 00 (Python would show it as a string \x03\x00\x00\x00\x0A\x00\x00\x00) And your file now looks like this - step value floats 03 00 00 00| 0A 00 00 00| 09 0B 21 CD ...^ -- read pos Okay, so now to read the floats. (steps, value) = struct.unpack(stepValPattern, bytes) #Converts 03 00 00 00 0A 00 00 00 to (3, 9) 9 chosen at random #steps equals 3 So now we substitute steps into the floatPattern floatPattern = %df % steps #floatPattern now equals 3f which is the same #struct pattern as fff bytesToRead = struct.calcsize(floatPattern) #bytesToRead is 12 bytes = f.read(bytesToRead) floatList = struct.unpack(floatPattern, bytes) Does that make sense? I hope so... but suffice to say - struct.calcsize() ensures cross platform compatibility... I tend not to use the endian identifier unless I'm dealing with a data source that will always, absolutely be a certain endianess, saves having to rejig your patterns for each different platform. And use f.read(x) for binary data. Regards, Liam Clarke ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] CPU Utilization
Thanks for your responses.
Michael Janssen wrote:
It's perhaps easier to read the information from the /proc filesystem
(this is where top gets it itself). man proc tells where the info is
stored (guess: /proc/stat).
stat does look in some ways easier. I will say that I found the
statistics somewhat baffling, but I'm sure it's all there.
Hugo González Monteverde wrote:
Hi,
top is very interactive so it would not be easy at all to parse.
Actually top has a batch mode. This works pretty well.
*def* xmlrpc_idlecpu(self):
u = commands.getoutput('top -b -n 1')
*return* u.split('\n')[2].split(',')[3]
I can suggest reading /proc/loadavg if you're in Linux.
proc(5) ('man 5 proc') says that /proc/loadavg is
The load average numbers give the number of jobs in
the run queue averaged over 1, 5 and 15 minutes.
They are the same as the load average numbers given
by uptime(1) and other programs.
It can be easily parsed with split()
That's an interesting idea to use that. Although if you have big jobs
and little jobs you might not know whether you can add another job to
that computer or not, because you would necessarily be attempting to
derive the utilization from those statistics.
Thank you both for your answers.
ds
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[Tutor] Returning multiple values from a script
Hi,
Can a script return multiple values to the os?
What I have in mind is something like the following:
1) Test.py
---
import sys
r = 7
sys.exit(r)
# What I really want to do is something along the lines of sys.exit(r,
Hans)
2) Script1.py (This script executes script test.py and prints out its
exit code):
--
import os
t = test.py
res = os.system('python test.py)
print res
Thanks,
Hans
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[Tutor] div_t
Hi, What is the usage of div_t in python? I have some unsigned integer variables and want to use ; div_tdiv_T; div_t div_N; div_t div_B; . . .. Best for all, Burge ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote:
Hi,
Can a script return multiple values to the os?
Is there a reason why you have to call the second test.py using
os.system()? I would write it to be imported and called.
test.py
--
def findR():
return 7, 'Hans'
script1.py
-
import test
res = test.findR()
print res
Kent
What I have in mind is something like the following:
1) Test.py
---
import sys
r = 7
sys.exit(r)
# What I really want to do is something along the lines of sys.exit(r,
Hans)
2) Script1.py (This script executes script test.py and prints out its
exit code):
--
import os
t = test.py
res = os.system('python test.py)
print res
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Re: [Tutor] div_t
At 02:59 PM 1/11/2006, Burge Kurt wrote: Hi, What is the usage of div_t in python? I have some unsigned integer variables and want to use ; div_t div_T; div_t div_N; div_t div_B; Your question is meaningless to me! Please clarify. div_t is not a Python constant or built_in. div_t div_T; is not a Python expression. Python integers are signed. Does any of this refer to another lannguage? ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Yes I agree that it'd be cleaner to import the second script and call
it.
The reason I'm keen to find a alternate method is that I have a whole
lot of scripts that were designed to run only as standalone scripts. ie
each of these scripts is not a function that I could just call from
another script. They are all of the format:
1) Test.py
---
import sys
sys.exit(5)
Now I'm trying to write a master script that'd run each one of these
scripts. I'm sure it would have been a lot easier if the scripts were of
the following format. Unfortunately they are not.:
Test.py
---
import sys
Def test():
return(5, Junk)
if __name__ == __main__:
test()
Well if there is no other way I think I'll have to alter all the scripts
to be of the above format. Just wondering if anyone has any suggestions
...
Cheers
Hans
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Kent Johnson
Sent: Thursday, 12 January 2006 12:06 p.m.
Cc: Python Tutor
Subject: Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote:
Hi,
Can a script return multiple values to the os?
Is there a reason why you have to call the second test.py using
os.system()? I would write it to be imported and called.
test.py
--
def findR():
return 7, 'Hans'
script1.py
-
import test
res = test.findR()
print res
Kent
What I have in mind is something like the following:
1) Test.py
---
import sys
r = 7
sys.exit(r)
# What I really want to do is something along the lines of sys.exit(r,
Hans)
2) Script1.py (This script executes script test.py and prints out its
exit code):
--
import os
t = test.py
res = os.system('python test.py)
print res
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Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote:
Yes I agree that it'd be cleaner to import the second script and call
it.
The reason I'm keen to find a alternate method is that I have a whole
lot of scripts that were designed to run only as standalone scripts. ie
each of these scripts is not a function that I could just call from
another script. They are all of the format:
1) Test.py
---
import sys
sys.exit(5)
Now I'm trying to write a master script that'd run each one of these
scripts. I'm sure it would have been a lot easier if the scripts were of
the following format. Unfortunately they are not.:
Test.py
---
import sys
Def test():
return(5, Junk)
if __name__ == __main__:
test()
Well if there is no other way I think I'll have to alter all the scripts
to be of the above format. Just wondering if anyone has any suggestions
ISTM that you have to change all the scripts anyway if you want to
return two values...why not change them to call a different function
(other than sys.exit) that does what you want? Do the scripts still have
to run standalone?
For example you could make a module mysys.py:
returnedvalue = None
def exit(value):
global returnedvalue
returnedvalue = value
Then just edit the scripts to import mysys and call mysys.exit(), run
the script with import and get the returnedvalue from mysys.
If you want a base hack that I couldn't possibly recommend :-) I suppose
you could replace sys.exit() with a function of your own choosing.
Something like this should work...
import sys
returnedvalue = None
def mysysexit(value):
... global returnedvalue
... returnedvalue = value
...
original_exit = sys.exit # if you need to keep the old value...
sys.exit = mysysexit
sys.exit(5) # here you can just import the module you want to run
returnedvalue
5
Isn't Python wonderful!
Kent
...
Cheers
Hans
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Kent Johnson
Sent: Thursday, 12 January 2006 12:06 p.m.
Cc: Python Tutor
Subject: Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote:
Hi,
Can a script return multiple values to the os?
Is there a reason why you have to call the second test.py using
os.system()? I would write it to be imported and called.
test.py
--
def findR():
return 7, 'Hans'
script1.py
-
import test
res = test.findR()
print res
Kent
What I have in mind is something like the following:
1) Test.py
---
import sys
r = 7
sys.exit(r)
# What I really want to do is something along the lines of sys.exit(r,
Hans)
2) Script1.py (This script executes script test.py and prints out its
exit code):
--
import os
t = test.py
res = os.system('python test.py)
print res
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Re: [Tutor] div_t
Burge Kurt wrote: Hi, What is the usage of div_t in python? I have some unsigned integer variables and want to use ; div_t div_T; div_t div_N; div_t div_B; I guess this is more C code. It doesn't have any Python equivalent - Python doesn't declare variables and doesn't have unsigned integers. You might be interested in the divmod() function: help(divmod) Help on built-in function divmod in module __builtin__: divmod(...) divmod(x, y) - (div, mod) Return the tuple ((x-x%y)/y, x%y). Invariant: div*y + mod == x. divmod(10, 3) (3, 1) You will in general get a better response from this list if you tell us what problem you are trying to solve, rather than showing brief snippets of C. Even better is to attempt a solution in Python and let us see where you get stuck. Have you read any of the tutorials I pointed out? Programming Python is quite different from C and you should try to get the flavor of it. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] calloc
Hi again (: How can I use calloc in python ? Before computing and processing my data I want to know how many bytes are available? Thanks in advance and best wishes, Burge ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Thanks for your reply Kent. Is it possible to dynamically import a module? The foll snippet of code throws an error ImportError: No module named testname t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] import %s%(testname) print testname.run_test() Any other means of importing dynamically? -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Kent Johnson Sent: Thursday, 12 January 2006 2:02 p.m. Cc: Python Tutor Subject: Re: [Tutor] Returning multiple values from a script Hans Dushanthakumar wrote: Yes I agree that it'd be cleaner to import the second script and call it. The reason I'm keen to find a alternate method is that I have a whole lot of scripts that were designed to run only as standalone scripts. ie each of these scripts is not a function that I could just call from another script. They are all of the format: 1) Test.py --- import sys sys.exit(5) Now I'm trying to write a master script that'd run each one of these scripts. I'm sure it would have been a lot easier if the scripts were of the following format. Unfortunately they are not.: Test.py --- import sys Def test(): return(5, Junk) if __name__ == __main__: test() Well if there is no other way I think I'll have to alter all the scripts to be of the above format. Just wondering if anyone has any suggestions ISTM that you have to change all the scripts anyway if you want to return two values...why not change them to call a different function (other than sys.exit) that does what you want? Do the scripts still have to run standalone? For example you could make a module mysys.py: returnedvalue = None def exit(value): global returnedvalue returnedvalue = value Then just edit the scripts to import mysys and call mysys.exit(), run the script with import and get the returnedvalue from mysys. If you want a base hack that I couldn't possibly recommend :-) I suppose you could replace sys.exit() with a function of your own choosing. Something like this should work... import sys returnedvalue = None def mysysexit(value): ... global returnedvalue ... returnedvalue = value ... original_exit = sys.exit # if you need to keep the old value... sys.exit = mysysexit sys.exit(5) # here you can just import the module you want to run returnedvalue 5 Isn't Python wonderful! Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Oops answered my own question. Dynamic importing is done using the __import__ function: t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] test = __import__(%s%(testname)) res = test.run_test() Cheers Hans -Original Message- From: Hans Dushanthakumar Sent: Thursday, 12 January 2006 2:28 p.m. Cc: Python Tutor Subject: RE: [Tutor] Returning multiple values from a script Thanks for your reply Kent. Is it possible to dynamically import a module? The foll snippet of code throws an error ImportError: No module named testname t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] import %s%(testname) print testname.run_test() Any other means of importing dynamically? -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Kent Johnson Sent: Thursday, 12 January 2006 2:02 p.m. Cc: Python Tutor Subject: Re: [Tutor] Returning multiple values from a script Hans Dushanthakumar wrote: Yes I agree that it'd be cleaner to import the second script and call it. The reason I'm keen to find a alternate method is that I have a whole lot of scripts that were designed to run only as standalone scripts. ie each of these scripts is not a function that I could just call from another script. They are all of the format: 1) Test.py --- import sys sys.exit(5) Now I'm trying to write a master script that'd run each one of these scripts. I'm sure it would have been a lot easier if the scripts were of the following format. Unfortunately they are not.: Test.py --- import sys Def test(): return(5, Junk) if __name__ == __main__: test() Well if there is no other way I think I'll have to alter all the scripts to be of the above format. Just wondering if anyone has any suggestions ISTM that you have to change all the scripts anyway if you want to return two values...why not change them to call a different function (other than sys.exit) that does what you want? Do the scripts still have to run standalone? For example you could make a module mysys.py: returnedvalue = None def exit(value): global returnedvalue returnedvalue = value Then just edit the scripts to import mysys and call mysys.exit(), run the script with import and get the returnedvalue from mysys. If you want a base hack that I couldn't possibly recommend :-) I suppose you could replace sys.exit() with a function of your own choosing. Something like this should work... import sys returnedvalue = None def mysysexit(value): ... global returnedvalue ... returnedvalue = value ... original_exit = sys.exit # if you need to keep the old value... sys.exit = mysysexit sys.exit(5) # here you can just import the module you want to run returnedvalue 5 Isn't Python wonderful! Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
On 12/01/06, Hans Dushanthakumar [EMAIL PROTECTED] wrote:
Any other means of importing dynamically?
There's an __import__ builtin. It's a function that takes a string and
returns the module.
eg:
sys = __import__('sys')
sys.platform
'win32'
[actually, it does a bit more than just that; read the docs]
--
John.
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Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote: Thanks for your reply Kent. Is it possible to dynamically import a module? The foll snippet of code throws an error ImportError: No module named testname t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] import %s%(testname) print testname.run_test() Any other means of importing dynamically? Well, it's not recommended, but the following will work (I'll leave the lectures on why it's not recommended to the more learned on the list ;-) ): eval(import %s % testname) -- Email: singingxduck AT gmail DOT com AIM: singingxduck Programming Python for the fun of it. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote: Oops answered my own question. Dynamic importing is done using the __import__ function: t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] test = __import__(%s%(testname)) res = test.run_test() Cheers Hans I think your method is less a Bad Idea (tm) than mine, so please disregard previous message. Cheers, Orri -- Email: singingxduck AT gmail DOT com AIM: singingxduck Programming Python for the fun of it. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Returning multiple values from a script
Hans Dushanthakumar wrote: Oops answered my own question. Dynamic importing is done using the __import__ function: t = [test1.py, test2.py] #Actually this list is filled in by a Tkinter Listbox selection. for f in t: testname = f[:-3] test = __import__(%s%(testname)) If testname is a string, as it is here, %s%(testname) has the same value as testname itself, you can just use __import__(testname) Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] calloc
On Thu, 12 Jan 2006, Burge Kurt wrote: How can I use calloc in python ? Before computing and processing my data I want to know how many bytes are available? Hi Burge, There's no concept of manual memory allocation in Python, and we don't have direct access to calloc/malloc/free. You're asking a lot of C-ish questions: have you looked through the Python Tutorial to get aquainted with the language yet? See: http://www.python.org/doc/tut/ One of the main distinctions between Python and C is that Python programming has a very dynamic feel to it. Program properties that may be static in other languages are fairly dynamic in Python. For example, rather than predefine a line buffer to read lines from a file, we use the readline() method of a file, which itself dynamically expands if the line is very long. The small program: ## file = open(/etc/passwd) for line in file: print line ## does what you might expect: it displays every line in the file. Note here that there are no hardcoded places where we've defined how long line must be. (An equivalent C program would be slightly more difficult to write unless we changed its semantics to read the file character-by-character or block-by-block where each unit is the same size, rather than line-by-line where each line's length can vary.) All the memory allocation and deallocation is handed by the Python runtime. Regions of memory that no longer are reachable are freed by garbage collection (or reference counting). This GC scheme reduces the chance of making silly memory-related errors such as double-free or memory leaking. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] declaring list
hello list I asked yesterday how we can declare an array in python. Thanks Brian van den Broek and Frank Schley for your responses. A[None] * n works for me. To answer Brian's question, I was writing the standard backtracking procedure to find the permutations of 1..n taken r at a time. def permutations (n, r): A, Used = [None] * (r+1), [False] * (n+1) def choose (m): if m r: print A[1:], else: for j in range (1, n+1): if not Used [j]: Used [j] = True A[m] = j choose (m+1) Used [j] = False choose (1) Thanks Logesh Pillay ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Finding the Index of a member of a Tuple
Hello everyone, I need to do something very simple but I'm having trouble finding the way to do it - at least easily. I have created a tuple and now need to find the position of individual members of that tuple. Specifically, the tuple is something like: words = (you, me, us, we, and, so, forth) and I need to be able to name a member, for example, us and find what the position (index) of that word is in the tuple. I would have thought there would be a simple built in functionfor that but I just went through the built in functions in the Python Library Reference and I didn't find anything. I could probably figure out how to write a whileloop or something to do a sequential search until I found the right member but I really believe there must be an easier way and I'm just not seeing it. You can probably tell I'm just learning Python so any help would be appreciated. Thanks very much in advance, Steve ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Finding the Index of a member of a Tuple
At 08:31 PM 1/11/2006, Steve Haley wrote: Hello everyone, I need to do something very simple but I'm having trouble finding the way to do it - at least easily. I have created a tuple and now need to find the position of individual members of that tuple. Specifically, the tuple is something like: words = (you, me, us, we, and, so, forth) and I need to be able to name a member, for example, us and find what the position (index) of that word is in the tuple. I would have thought there would be a simple built in function for that but I just went through the built in functions in the Python Library Reference and I didn't find anything. I could probably figure out how to write a while loop or something to do a sequential search until I found the right member but I really believe there must be an easier way and I'm just not seeing it. You can probably tell I'm just learning Python so any help would be appreciated. Unfortunately there is no list method find. Sigh. Here's how I'd do it: # create a dictionary with each word as key and ordinal as value words = dict([(n,m) for m,n in enumerate((you, me, us, we, and, so, forth))]) words[me] # returns 1 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] calloc
On Thu, 12 Jan 2006, Burge Kurt wrote: Again thank you :( and sorry for asking that much questions in one day and I know most of them were nonsense .. Don't worry about it; please feel free to continue to ask questions on the list. It wasn't quite clear what experience you had before: I have to assume that you've had a lot of C, but other than that, I'm quite clueless. I read the tutorial and still forget lots of parts again and again reading it! I feel mixed about recommending the official Python Tutotrial: it goes way too fast for my tastes. I pointed it out just because it's probably the quickest way to get a taste of the language, but it's not substantial. I'd instead recommend a different tutorial; there are several listed from the link here: http://wiki.python.org/moin/BeginnersGuide/Programmers I think that Dive into Python is especially good, but of course, whatever tutorial there that reads easiest for you is best. Good luck to you! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Locating directory of script?
Hi all, Let's say I have a script called bob.py in a directory called c:\pythonstuff, which is in my PATH env_var, and python is also in my PATH, and from a completely different directory I call python bob.py is there a right way to determine what directory bob.py resides in? So far I've found that import inspect class Foo: pass sourceP = inspect.getsourcefile(Foo) works, but I'm not too sure how resilient that is... Regards, Liam Clarke ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Finding the Index of a member of a Tuple
bob said unto the world upon 11/01/06 10:47 PM: At 08:31 PM 1/11/2006, Steve Haley wrote: Hello everyone, I need to do something very simple but I'm having trouble finding the way to do it - at least easily. I have created a tuple and now need to find the position of individual members of that tuple. Specifically, the tuple is something like: words = (you, me, us, we, and, so, forth) and I need to be able to name a member, for example, us and find what the position (index) of that word is in the tuple. I would have thought there would be a simple built in function for that but I just went through the built in functions in the Python Library Reference and I didn't find anything. I could probably figure out how to write a while loop or something to do a sequential search until I found the right member but I really believe there must be an easier way and I'm just not seeing it. You can probably tell I'm just learning Python so any help would be appreciated. Unfortunately there is no list method find. Sigh. Here's how I'd do it: # create a dictionary with each word as key and ordinal as value words = dict([(n,m) for m,n in enumerate((you, me, us, we, and, so, forth))]) words[me] # returns 1 I assume Bob meant that tuples have no index or find method. His suggested procedure will work, but it seems more work than: t = (I'm, a, tuple., I, have, only, magic, methods.) l = list(t) l.index(have) 4 t[4] 'have' I say more work as the way above builds a list to turn into a dictionary. But, since dictionary access is fast, it might be quicker for long tuples where the sought item is near then end. If it matters, test. HTH, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Locating directory of script?
Liam Clarke said unto the world upon 12/01/06 12:32 AM: Hi all, Let's say I have a script called bob.py in a directory called c:\pythonstuff, which is in my PATH env_var, and python is also in my PATH, and from a completely different directory I call python bob.py is there a right way to determine what directory bob.py resides in? So far I've found that import inspect class Foo: pass sourceP = inspect.getsourcefile(Foo) works, but I'm not too sure how resilient that is... Regards, Liam Clarke Hey Liam, import this The Zen of Python, by Tim Peters snip the wisdom this.__file__ '/usr/lib/python2.4/this.pyc' HTH, Brian vdB ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Finding the Index of a member of a Tuple
On Wed, 11 Jan 2006, Steve Haley wrote: I need to do something very simple but I'm having trouble finding the way to do it - at least easily. I have created a tuple and now need to find the position of individual members of that tuple. Specifically, the tuple is something like: words = (you, me, us, we, and, so, forth) and I need to be able to name a member, for example, us and find what the position (index) of that word is in the tuple. Does it have to be a tuple? If you make it a list, you can use index(): words = [you, me, us, we, and, so, forth] words.index(and) 4 If it must be a tuple, you can't do that directly: words = (you, me, us, we, and, so, forth) words.index(and) Traceback (most recent call last): File stdin, line 1, in ? AttributeError: 'tuple' object has no attribute 'index' but you can wrap it in a list conversion: words = (you, me, us, we, and, so, forth) list(words).index(and) 4 I'm not sure why tuple wouldn't have this capability; but it doesn't. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
