filecmp.py 文件源码

def cmp(f1, f2, shallow=1):
    """Compare two files.

    Arguments:

    f1 -- First file name

    f2 -- Second file name

    shallow -- Just check stat signature (do not read the files).
               defaults to 1.

    Return value:

    True if the files are the same, False otherwise.

    This function uses a cache for past comparisons and the results,
    with a cache invalidation mechanism relying on stale signatures.

    """

    s1 = _sig(os.stat(f1))
    s2 = _sig(os.stat(f2))
    if s1[0] != stat.S_IFREG or s2[0] != stat.S_IFREG:
        return False
    if shallow and s1 == s2:
        return True
    if s1[1] != s2[1]:
        return False

    outcome = _cache.get((f1, f2, s1, s2))
    if outcome is None:
        outcome = _do_cmp(f1, f2)
        if len(_cache) > 100:      # limit the maximum size of the cache
            _cache.clear()
        _cache[f1, f2, s1, s2] = outcome
    return outcome