Python Regex Question

exception.txt

Traceback (most recent call last):
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/functools.py", line 176, in wrapper
    result = cache[key]
KeyError: (<class 'str'>, '(^.*def\\W*)(\\w+)\\W*\\((.*)?\\):', 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./pickout_fn_defs.py", line 25, in <module>
    FnDefRe = re.compile(r'(^.*def\W*)(\w+)\W*\((.*)?\):')
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/re.py", line 206, in compile
    return _compile(pattern, flags)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/re.py", line 255, in _compile
    return _compile_typed(type(pattern), pattern, flags)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/functools.py", line 180, in wrapper
    result = user_function(*args, **kwds)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/re.py", line 267, in _compile_typed
    return sre_compile.compile(pattern, flags)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/sre_compile.py", line 495, in compile
    code = _code(p, flags)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/sre_compile.py", line 480, in _code
    _compile(code, p.data, flags)
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/sre_compile.py", line 74, in _compile
    elif _simple(av) and op is not REPEAT:
  File "/usr/local/bin/../Cellar/python3/3.2.2/lib/python3.2/sre_compile.py", line 359, in _simple
    raise error("nothing to repeat")
sre_constants.error: nothing to repeat

full_script.py

#!/usr/bin/env python3

import os
import os.path
import sys
import re


def read_filename():
    while True:
        filename = input('Enter filename: ' )
        if os.path.exists(filename):
            print('Found file ' + filename)
            break
        print('Did not find file ' + filename + '. Try again')
    return filename

def printFnName(mLine):
    print("Function: ", mLine.group(2))

def printArgs(mLine):
    for arg in re.split(',', mLine.group(3)):
        print("Arg: ", arg)

FnDefRe = re.compile(r'(^.*def\W*)(\w+)\W*\((.*)?\):')
# group-1 is 'def', group-2 is the fn name, group-3 are the args
#
def matchDefLine(line):
    return FnDefRe.match(line)

def process_all_lines(filename):
    f = open(filename)
    i = 1
    lineLst = f.read().split('\n')
    for line in lineLst:
        #print(line)
        mLine = matchDefLine(line)
        if mLine:
            print('---')
            printFnName(mLine)
            printArgs(mLine)
        #--
        i = i + 1
    f.close()

def main():
    filename = read_filename()
    print ('Filename = ' + filename)
    print ('Processing file ' + filename)
    process_all_lines(filename)

if __name__ == "__main__":
    main()

py_re.py

# This one works, it was the regex as it was given to us
FnDefRe = re.compile(r'(^.*def\W*)(\w+)\W*\((.*)\):') 

# This one does not work, throws an exception
FnDefRe = re.compile(r'(^.*def\W*)(\w+)\W*\((.*)?\):')