cpython/Lib/lib2to3/fixes/fix_map.py

93 lines
2.9 KiB
Python

# Copyright 2007 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.
"""Fixer that changes map(F, ...) into list(map(F, ...)) unless there
exists a 'from future_builtins import map' statement in the top-level
namespace.
As a special case, map(None, X) is changed into list(X). (This is
necessary because the semantics are changed in this case -- the new
map(None, X) is equivalent to [(x,) for x in X].)
We avoid the transformation (except for the special case mentioned
above) if the map() call is directly contained in iter(<>), list(<>),
tuple(<>), sorted(<>), ...join(<>), or for V in <>:.
NOTE: This is still not correct if the original code was depending on
map(F, X, Y, ...) to go on until the longest argument is exhausted,
substituting None for missing values -- like zip(), it now stops as
soon as the shortest argument is exhausted.
"""
# Local imports
from ..pgen2 import token
from . import basefix
from .util import Name, Call, ListComp, does_tree_import, in_special_context
from ..pygram import python_symbols as syms
class FixMap(basefix.BaseFix):
PATTERN = """
map_none=power<
'map'
trailer< '(' arglist< 'None' ',' arg=any [','] > ')' >
>
|
map_lambda=power<
'map'
trailer<
'('
arglist<
lambdef< 'lambda'
(fp=NAME | vfpdef< '(' fp=NAME ')'> ) ':' xp=any
>
','
it=any
>
')'
>
>
|
power<
'map'
args=trailer< '(' [any] ')' >
>
"""
def start_tree(self, *args):
super(FixMap, self).start_tree(*args)
self._future_map_found = None
def has_future_map(self, node):
if self._future_map_found is not None:
return self._future_map_found
self._future_map_found = does_tree_import('future_builtins', 'map', node)
return self._future_map_found
def transform(self, node, results):
if self.has_future_map(node):
# If a future map has been imported for this file, we won't
# be making any modifications
return
if node.parent.type == syms.simple_stmt:
self.warning(node, "You should use a for loop here")
new = node.clone()
new.set_prefix("")
new = Call(Name("list"), [new])
elif "map_lambda" in results:
new = ListComp(results.get("xp").clone(),
results.get("fp").clone(),
results.get("it").clone())
else:
if "map_none" in results:
new = results["arg"].clone()
else:
if in_special_context(node):
return None
new = node.clone()
new.set_prefix("")
new = Call(Name("list"), [new])
new.set_prefix(node.get_prefix())
return new