Return a list of imported Python modules used in a script?

Question

I am writing a program that categorizes a list of Python files by which modules they import. As such I need to scan the collection of .py files ad return a list of which mod

Answer 1

I'm editing my original answer to say this. This is doable with a code snippet like the one below, but parsing the AST may be the best way to go.

def iter_imports(fd):
    """ Yield only lines that appear to be imports from an iterable.
        fd can be an open file, a list of lines, etc.
    """
    for line in fd:
        trimmed = line.strip()
        if trimmed.startswith('import '):
            yield trimmed
        elif trimmed.startswith('from ') and ('import ' in trimmed):
            yield trimmed

def main():
    # File name to read.
    filename = '/my/path/myfile.py'
    # Safely open the file, exit on error
    try:
        with open(filename) as f:
            # Iterate over the lines in this file, and generate a list of
            # lines that appear to be imports.
            import_lines = list(iter_imports(f))
    except (IOError, OSError) as exIO:
        print('Error opening file: {}\n{}'.format(filename, exIO))
        return 1
    else:
        # From here, import_lines should be a list of lines like this:
        #     from module import thing
        #     import os, sys
        #     from module import *
        # Do whatever you need to do with the import lines.
        print('\n'.join(import_lines))

    return 0

if __name__ == '__main__':
    sys.exit(main())

Further string parsing will be needed to grab just the module names. This does not catch cases where multi-line strings or doc strings contain the words 'import ' or 'from X import '. This is why I suggested parsing the AST.