Python: NameError: free variable 're' referenced before assignment in enclosing scope -

i have strange nameerror in python 3.3.1 (win7).

the code:

import re  # ...  # parse exclude patterns. excluded_regexps = set(re.compile(regexp) regexp in options.exclude_pattern)  # line 561: excluded_regexps |= set(re.compile(regexp, re.i) regexp in options.exclude_pattern_ci) 

the error:

traceback (most recent call last):   file "py3createtorrent.py", line 794, in <module>     sys.exit(main(sys.argv))   file "py3createtorrent.py", line 561, in main     excluded_regexps |= set(re.compile(regexp, re.i) regexp in options.exclude_pattern_ci)   file "py3createtorrent.py", line 561, in <genexpr>     excluded_regexps |= set(re.compile(regexp, re.i) regexp in options.exclude_pattern_ci) nameerror: free variable 're' referenced before assignment in enclosing scope 

note line 561, error occurs, second line in code above. in other words: re not free variable. regular expression module , can referenced fine in first line.

it seems me reference re.i causing problem, don't see how.

most likely, assigning re (presumably inadvertently) @ point below line 561, in same function. reproduces error:

import re  def main():     term = re.compile("foo")     re = 0  main()