source: python/vendor/Python-2.7.6/Tools/scripts/findnocoding.py

#!/usr/bin/env python

"""List all those Python files that require a coding directive

Usage: nocoding.py dir1 [dir2...]
"""

__author__ = "Oleg Broytmann, Georg Brandl"

import sys, os, re, getopt

# our pysource module finds Python source files
try:
    import pysource
except ImportError:
    # emulate the module with a simple os.walk
    class pysource:
        has_python_ext = looks_like_python = can_be_compiled = None
        def walk_python_files(self, paths, *args, **kwargs):
            for path in paths:
                if os.path.isfile(path):
                    yield path.endswith(".py")
                elif os.path.isdir(path):
                    for root, dirs, files in os.walk(path):
                        for filename in files:
                            if filename.endswith(".py"):
                                yield os.path.join(root, filename)
    pysource = pysource()


    print >>sys.stderr, ("The pysource module is not available; "
                         "no sophisticated Python source file search will be done.")


decl_re = re.compile(r'^[ \t\f]*#.*coding[:=][ \t]*([-\w.]+)')

def get_declaration(line):
    match = decl_re.match(line)
    if match:
        return match.group(1)
    return b''

def has_correct_encoding(text, codec):
    try:
        unicode(text, codec)
    except UnicodeDecodeError:
        return False
    else:
        return True

def needs_declaration(fullpath):
    try:
        infile = open(fullpath, 'rU')
    except IOError: # Oops, the file was removed - ignore it
        return None

    line1 = infile.readline()
    line2 = infile.readline()

    if get_declaration(line1) or get_declaration(line2):
        # the file does have an encoding declaration, so trust it
        infile.close()
        return False

    # check the whole file for non-ASCII characters
    rest = infile.read()
    infile.close()

    if has_correct_encoding(line1+line2+rest, "ascii"):
        return False

    return True


usage = """Usage: %s [-cd] paths...
    -c: recognize Python source files trying to compile them
    -d: debug output""" % sys.argv[0]

try:
    opts, args = getopt.getopt(sys.argv[1:], 'cd')
except getopt.error, msg:
    print >>sys.stderr, msg
    print >>sys.stderr, usage
    sys.exit(1)

is_python = pysource.looks_like_python
debug = False

for o, a in opts:
    if o == '-c':
        is_python = pysource.can_be_compiled
    elif o == '-d':
        debug = True

if not args:
    print >>sys.stderr, usage
    sys.exit(1)

for fullpath in pysource.walk_python_files(args, is_python):
    if debug:
        print "Testing for coding: %s" % fullpath
    result = needs_declaration(fullpath)
    if result:
        print fullpath