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How would you make the give code more Pythonic?

I want to get Paths out of the sample like /usr/local/sources/devel/algebra.py: def _alg(...) without the character :.

My code

import os
FunctionPath = "/usr/local/sources/devel/sage-main/build/sage/"
cmd = "grep -R 'def ' %s | cut -d' ' -f1" % (FunctionPath)
cmd += ' &'
raw_path = os.system(cmd)
path = raw_path.replace(':', '')       // not working

print path

[edit]: The code cannot be written pythonically only with Built-in functions.

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  • 2
    Who says that it can be written using only built-ins? Maybe the person meant that it can be done using only the Standard Python Library. Commented Dec 22, 2009 at 14:36
  • 2
    I agree with mikej. It is extremely unpythonic to not use built-in libraries. Batteries are included for a reason. Commented Dec 22, 2009 at 14:41
  • O(n^3)?? :-| I cannot see where do you get that. Commented Dec 22, 2009 at 14:42
  • 1
    btw what are you trying to achieve? t Commented Dec 22, 2009 at 14:46
  • 1
    Libraries or no libraries, punting out to the shell to do simple data processing tasks is definitely unpythonic, makes error handling hard, and includes many string-escaping pitfalls with potentially security-sensitive consequences. If you must do it, use the subprocess module to take care of most of the argument-escaping stuff. But there's certainly no need to resort to the shell for such trivial string slicing as this. Commented Dec 22, 2009 at 15:18

4 Answers 4

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11

Why not do this:

for line in open(FunctionPath):
    line = line.strip()
    if line.startswith('def '):
        print '%s: %s' % (FunctionPath, line.partition(':')[0])

And if you use fileinput module you can iterate over lines from multiple input streams very easily:

import fileinput
for line in fileinput.input(paths):
    line = line.strip()
    if line.startswith('def '):
        print '%s: %s' % (fileinput.filename(), line.partition(':')[0])

BTW, if you don't give fileinput.input any path it will use sys.argv by default, so you can run your python script like this:

$ python script.py filepath1 filepath2 filepath3

fileinput will read the files for you.

if you really want to cover all cases, you shouldn't be using replace(':', '') because it is possible to have 

def func(): #comment myfunc():
   pass

The following will give you the correct result:

>>> 'def func(): #comment myfunc():'.partition(':')[0]
'def func()'

Unless you want the comment as well.

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Comments

1

Literaly: "without the modules os, subprocess or Popen"

You can also use commands module :P

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1

If you're using Python mainly as a wrapper to sh, why not doing everything directly from the shell?

set SEARCH_PATH=/usr/local/sources/devel/sage-main/build/sage/
grep -R 'def ' $SEARCH_PATH | awk -F':' '{print $1 $2}'
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1 Comment

I agree with you. It is easiest to use shell. The part could also be with | cut -d' ' -f1 | sed s,:,,g. Forgot sed when asking this question :)
1

Same with os.walk

for path, dirnames, filenames in os.walk(function_path):
    for filename in filenames:
        path = os.path.join(path, filename)
        with open(path) as f:
             for line in f:
                 # Instead of grep
                 if 'def ' in line:
                       # Instead of cut
                       data = line.split(' ')[2]
                       print data.replace(":", '')
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