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 modules they import. As an example, if one of the files I import has the following lines:

import os
import sys, gtk

I would like it to return:

["os", "sys", "gtk"]

I played with modulefinder and wrote:

from modulefinder import ModuleFinder

finder = ModuleFinder()
finder.run_script('testscript.py')

print 'Loaded modules:'
for name, mod in finder.modules.iteritems():
    print '%s ' % name,

but this returns more than just the modules used in the script. As an example in a script which merely has:

import os
print os.getenv('USERNAME')

The modules returned from the ModuleFinder script return:

tokenize  heapq  __future__  copy_reg  sre_compile  _collections  cStringIO  _sre  functools  random  cPickle  __builtin__  subprocess  cmd  gc  __main__  operator  array  select  _heapq  _threading_local  abc  _bisect  posixpath  _random  os2emxpath  tempfile  errno  pprint  binascii  token  sre_constants  re  _abcoll  collections  ntpath  threading  opcode  _struct  _warnings  math  shlex  fcntl  genericpath  stat  string  warnings  UserDict  inspect  repr  struct  sys  pwd  imp  getopt  readline  copy  bdb  types  strop  _functools  keyword  thread  StringIO  bisect  pickle  signal  traceback  difflib  marshal  linecache  itertools  dummy_thread  posix  doctest  unittest  time  sre_parse  os  pdb  dis

...whereas I just want it to return 'os', as that was the module used in the script.

Can anyone help me achieve this?

UPDATE: I just want to clarify that I would like to do this without running the Python file being analyzed, and just scanning the code.

Answer 1

IMO the best way todo this is to use the http://furius.ca/snakefood/ package. The author has done all of the required work to get not only directly imported modules but it uses the AST to parse the code for runtime dependencies that a more static analysis would miss.

Worked up a command example to demonstrate:

sfood ./example.py | sfood-cluster > example.deps

That will generate a basic dependency file of each unique module. For even more detail use:

sfood -r -i ./example.py | sfood-cluster > example.deps

To walk a tree and find all imports, you can also do this in code: Please NOTE - The AST chunks of this routine were lifted from the snakefood source which has this copyright: Copyright (C) 2001-2007 Martin Blais. All Rights Reserved.

 import os
 import compiler
 from compiler.ast import Discard, Const
 from compiler.visitor import ASTVisitor

 def pyfiles(startPath):
     r = []
     d = os.path.abspath(startPath)
     if os.path.exists(d) and os.path.isdir(d):
         for root, dirs, files in os.walk(d):
             for f in files:
                 n, ext = os.path.splitext(f)
                 if ext == '.py':
                     r.append([d, f])
     return r

 class ImportVisitor(object):
     def __init__(self):
         self.modules = []
         self.recent = []
     def visitImport(self, node):
         self.accept_imports()
         self.recent.extend((x[0], None, x[1] or x[0], node.lineno, 0)
                            for x in node.names)
     def visitFrom(self, node):
         self.accept_imports()
         modname = node.modname
         if modname == '__future__':
             return # Ignore these.
         for name, as_ in node.names:
             if name == '*':
                 # We really don't know...
                 mod = (modname, None, None, node.lineno, node.level)
             else:
                 mod = (modname, name, as_ or name, node.lineno, node.level)
             self.recent.append(mod)
     def default(self, node):
         pragma = None
         if self.recent:
             if isinstance(node, Discard):
                 children = node.getChildren()
                 if len(children) == 1 and isinstance(children[0], Const):
                     const_node = children[0]
                     pragma = const_node.value
         self.accept_imports(pragma)
     def accept_imports(self, pragma=None):
         self.modules.extend((m, r, l, n, lvl, pragma)
                             for (m, r, l, n, lvl) in self.recent)
         self.recent = []
     def finalize(self):
         self.accept_imports()
         return self.modules

 class ImportWalker(ASTVisitor):
     def __init__(self, visitor):
         ASTVisitor.__init__(self)
         self._visitor = visitor
     def default(self, node, *args):
         self._visitor.default(node)
         ASTVisitor.default(self, node, *args) 

 def parse_python_source(fn):
     contents = open(fn, 'rU').read()
     ast = compiler.parse(contents)
     vis = ImportVisitor() 

     compiler.walk(ast, vis, ImportWalker(vis))
     return vis.finalize()

 for d, f in pyfiles('/Users/bear/temp/foobar'):
     print d, f
     print parse_python_source(os.path.join(d, f))