/usr/lib/python2.7/compiler/future.py is in libpython2.7-stdlib 2.7.6-8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | """Parser for future statements
"""
from compiler import ast, walk
def is_future(stmt):
    """Return true if statement is a well-formed future statement"""
    if not isinstance(stmt, ast.From):
        return 0
    if stmt.modname == "__future__":
        return 1
    else:
        return 0
class FutureParser:
    features = ("nested_scopes", "generators", "division",
                "absolute_import", "with_statement", "print_function",
                "unicode_literals")
    def __init__(self):
        self.found = {} # set
    def visitModule(self, node):
        stmt = node.node
        for s in stmt.nodes:
            if not self.check_stmt(s):
                break
    def check_stmt(self, stmt):
        if is_future(stmt):
            for name, asname in stmt.names:
                if name in self.features:
                    self.found[name] = 1
                else:
                    raise SyntaxError, \
                          "future feature %s is not defined" % name
            stmt.valid_future = 1
            return 1
        return 0
    def get_features(self):
        """Return list of features enabled by future statements"""
        return self.found.keys()
class BadFutureParser:
    """Check for invalid future statements"""
    def visitFrom(self, node):
        if hasattr(node, 'valid_future'):
            return
        if node.modname != "__future__":
            return
        raise SyntaxError, "invalid future statement " + repr(node)
def find_futures(node):
    p1 = FutureParser()
    p2 = BadFutureParser()
    walk(node, p1)
    walk(node, p2)
    return p1.get_features()
if __name__ == "__main__":
    import sys
    from compiler import parseFile, walk
    for file in sys.argv[1:]:
        print file
        tree = parseFile(file)
        v = FutureParser()
        walk(tree, v)
        print v.found
        print
 |