如何在python中获取给定源文件和相关源文件的哈希？

Question

我有一个源文件，比如a.py，它导入了b.py 和一些内置模块。 b.py 可能会进一步导入c.py 和d.py 等。在a.py 中，有一个缓慢的操作会生成一个对象作为结果。为了提高速度，我使用pickle 模块转储生成的对象，如果之前生成过，则加载。

但是，如果修改了a、b、c、d 源代码中的任何一个，则应重新生成对象。为了避免每次手动删除泡菜文件，我想计算源的哈希并将其写入泡菜文件。所以我可以检查哈希码并决定是否生成对象。

如何编写一个函数，如果给定a.py，它将递归找到b.py、c.py和d.py，并一起计算哈希码？

有没有更好的方法来处理这个问题？

Answer 1

你可以这样做：

import sys
for name, module in sys.modules.iteritems():
    # module object is a representation of imported module
    try:
        # Next line shows how to access path of Python module file
        module.__file__ 
    except AttributeError:
        '''
        Built-in modules and other special cases don't have __file__
        attribute but you shouldn't care about them as their behaviour won't change
        '''

现在您可以计算和比较您的哈希值。但老实说，我会说比较文件修改时间比计算哈希值足够且便宜。

print sys.modules 在我的例子中的输出是：

{'copy_reg': <module 'copy_reg' from '/usr/lib64/python2.7/copy_reg.pyc'>, 'sre_compile': <module 'sre_compile' from '/usr/lib64/python2.7/sre_compile.pyc'>, '_sre': <module '_sre' (built-in)>, 'encodings': <module 'encodings' from '/usr/lib64/python2.7/encodings/__init__.pyc'>, 'site': <module 'site' from '/usr/lib64/python2.7/site.pyc'>, '__builtin__': <module '__builtin__' (built-in)>, 'sysconfig': <module 'sysconfig' from '/usr/lib64/python2.7/sysconfig.pyc'>, 'atexit': <module 'atexit' from '/usr/lib64/python2.7/atexit.pyc'>, '__main__': <module '__main__' (built-in)>, 'encodings.encodings': None, 'abc': <module 'abc' from '/usr/lib64/python2.7/abc.pyc'>, 'posixpath': <module 'posixpath' from '/usr/lib64/python2.7/posixpath.pyc'>, '_weakrefset': <module '_weakrefset' from '/usr/lib64/python2.7/_weakrefset.pyc'>, 'errno': <module 'errno' (built-in)>, 'encodings.codecs': None, 'sre_constants': <module 'sre_constants' from '/usr/lib64/python2.7/sre_constants.pyc'>, 're': <module 're' from '/usr/lib64/python2.7/re.pyc'>, '_abcoll': <module '_abcoll' from '/usr/lib64/python2.7/_abcoll.pyc'>, 'types': <module 'types' from '/usr/lib64/python2.7/types.pyc'>, '_codecs': <module '_codecs' (built-in)>, 'encodings.__builtin__': None, '_warnings': <module '_warnings' (built-in)>, 'genericpath': <module 'genericpath' from '/usr/lib64/python2.7/genericpath.pyc'>, 'stat': <module 'stat' from '/usr/lib64/python2.7/stat.pyc'>, 'zipimport': <module 'zipimport' (built-in)>, '_sysconfigdata': <module '_sysconfigdata' from '/usr/lib64/python2.7/_sysconfigdata.pyc'>, 'warnings': <module 'warnings' from '/usr/lib64/python2.7/warnings.pyc'>, 'UserDict': <module 'UserDict' from '/usr/lib64/python2.7/UserDict.pyc'>, 'encodings.utf_8': <module 'encodings.utf_8' from '/usr/lib64/python2.7/encodings/utf_8.pyc'>, 'sys': <module 'sys' (built-in)>, 'codecs': <module 'codecs' from '/usr/lib64/python2.7/codecs.pyc'>, 'readline': <module 'readline' from '/usr/lib64/python2.7/lib-dynload/readline.so'>, 'os.path': <module 'posixpath' from '/usr/lib64/python2.7/posixpath.pyc'>, '_locale': <module '_locale' from '/usr/lib64/python2.7/lib-dynload/_locale.so'>, 'rlcompleter': <module 'rlcompleter' from '/usr/lib64/python2.7/rlcompleter.pyc'>, 'signal': <module 'signal' (built-in)>, 'traceback': <module 'traceback' from '/usr/lib64/python2.7/traceback.pyc'>, 'linecache': <module 'linecache' from '/usr/lib64/python2.7/linecache.pyc'>, 'posix': <module 'posix' (built-in)>, 'encodings.aliases': <module 'encodings.aliases' from '/usr/lib64/python2.7/encodings/aliases.pyc'>, 'exceptions': <module 'exceptions' (built-in)>, 'sre_parse': <module 'sre_parse' from '/usr/lib64/python2.7/sre_parse.pyc'>, 'os': <module 'os' from '/usr/lib64/python2.7/os.pyc'>, '_weakref': <module '_weakref' (built-in)>}

编辑：

怎么样：

import sys
import copy

# Save the dict of imported modules
modules_before = copy.copy(sys.modules)

# Import b, which will import c and d and so on
import b

for name, module in sys.modules.iteritems():
    if name in modules_before:
        # Skip irrelevant modules
        continue
    # module object is a representation of imported module
    try:
        # Next line shows how to access path of Python module file
        module.__file__ 
    except AttributeError:
        '''
        Built-in modules and other special cases don't have __file__
        attribute but you shouldn't care about them as their behaviour won't change
        '''