cpython/Lib/lib2to3/fixes/fix_ws_comma.py

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"""Fixer that changes 'a ,b' into 'a, b'.
This also changes '{a :b}' into '{a: b}', but does not touch other
uses of colons. It does not touch other uses of whitespace.
"""
from .. import pytree
from ..pgen2 import token
from .import basefix
class FixWsComma(basefix.BaseFix):
explicit = True # The user must ask for this fixers
PATTERN = """
any<(not(',') any)+ ',' ((not(',') any)+ ',')* [not(',') any]>
"""
COMMA = pytree.Leaf(token.COMMA, ",")
COLON = pytree.Leaf(token.COLON, ":")
SEPS = (COMMA, COLON)
def transform(self, node, results):
new = node.clone()
comma = False
for child in new.children:
if child in self.SEPS:
prefix = child.get_prefix()
if prefix.isspace() and "\n" not in prefix:
child.set_prefix("")
comma = True
else:
if comma:
prefix = child.get_prefix()
if not prefix:
child.set_prefix(" ")
comma = False
return new