Current File : //lib/python3.10/lib2to3/fixes/fix_map.py
# 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 fixer_base
from ..fixer_util import Name, ArgList, Call, ListComp, in_special_context
from ..pygram import python_symbols as syms
from ..pytree import Node
class FixMap(fixer_base.ConditionalFix):
BM_compatible = True
PATTERN = """
map_none=power<
'map'
trailer< '(' arglist< 'None' ',' arg=any [','] > ')' >
[extra_trailers=trailer*]
>
|
map_lambda=power<
'map'
trailer<
'('
arglist<
lambdef< 'lambda'
(fp=NAME | vfpdef< '(' fp=NAME ')'> ) ':' xp=any
>
','
it=any
>
')'
>
[extra_trailers=trailer*]
>
|
power<
'map' args=trailer< '(' [any] ')' >
[extra_trailers=trailer*]
>
"""
skip_on = 'future_builtins.map'
def transform(self, node, results):
if self.should_skip(node):
return
trailers = []
if 'extra_trailers' in results:
for t in results['extra_trailers']:
trailers.append(t.clone())
if node.parent.type == syms.simple_stmt:
self.warning(node, "You should use a for loop here")
new = node.clone()
new.prefix = ""
new = Call(Name("list"), [new])
elif "map_lambda" in results:
new = ListComp(results["xp"].clone(),
results["fp"].clone(),
results["it"].clone())
new = Node(syms.power, [new] + trailers, prefix="")
else:
if "map_none" in results:
new = results["arg"].clone()
new.prefix = ""
else:
if "args" in results:
args = results["args"]
if args.type == syms.trailer and \
args.children[1].type == syms.arglist and \
args.children[1].children[0].type == token.NAME and \
args.children[1].children[0].value == "None":
self.warning(node, "cannot convert map(None, ...) "
"with multiple arguments because map() "
"now truncates to the shortest sequence")
return
new = Node(syms.power, [Name("map"), args.clone()])
new.prefix = ""
if in_special_context(node):
return None
new = Node(syms.power, [Name("list"), ArgList([new])] + trailers)
new.prefix = ""
new.prefix = node.prefix
return new
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