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      1 """Fixer that changes 'a ,b' into 'a, b'.
      2 
      3 This also changes '{a :b}' into '{a: b}', but does not touch other
      4 uses of colons.  It does not touch other uses of whitespace.
      5 
      6 """
      7 
      8 from .. import pytree
      9 from ..pgen2 import token
     10 from .. import fixer_base
     11 
     12 class FixWsComma(fixer_base.BaseFix):
     13 
     14     explicit = True # The user must ask for this fixers

     15 
     16     PATTERN = """
     17     any<(not(',') any)+ ',' ((not(',') any)+ ',')* [not(',') any]>
     18     """
     19 
     20     COMMA = pytree.Leaf(token.COMMA, u",")
     21     COLON = pytree.Leaf(token.COLON, u":")
     22     SEPS = (COMMA, COLON)
     23 
     24     def transform(self, node, results):
     25         new = node.clone()
     26         comma = False
     27         for child in new.children:
     28             if child in self.SEPS:
     29                 prefix = child.prefix
     30                 if prefix.isspace() and u"\n" not in prefix:
     31                     child.prefix = u""
     32                 comma = True
     33             else:
     34                 if comma:
     35                     prefix = child.prefix
     36                     if not prefix:
     37                         child.prefix = u" "
     38                 comma = False
     39         return new
     40