Lib/lib2to3/fixes/fix_paren.py

   1 """Fixer that addes parentheses where they are required
   2
   3 This converts ``[x for x in 1, 2]`` to ``[x for x in (1, 2)]``."""
   4
   5 # By Taek Joo Kim and Benjamin Peterson
   6
   7 # Local imports
   8 from .. import fixer_base
   9 from ..fixer_util import LParen, RParen
  10
  11 # XXX This doesn't support nested for loops like [x for x in 1, 2 for x in 1, 2]
  12 class FixParen(fixer_base.BaseFix):
  13     PATTERN = """
  14         atom< ('[' | '(')
  15             (listmaker< any
  16                 comp_for<
  17                     'for' NAME 'in'
  18                     target=testlist_safe< any (',' any)+ [',']
  19                      >
  20                     [any]
  21                 >
  22             >
  23             |
  24             testlist_gexp< any
  25                 comp_for<
  26                     'for' NAME 'in'
  27                     target=testlist_safe< any (',' any)+ [',']
  28                      >
  29                     [any]
  30                 >
  31             >)
  32         (']' | ')') >
  33     """
  34
  35     def transform(self, node, results):
  36         target = results["target"]
  37
  38         lparen = LParen()
  39         lparen.prefix = target.prefix
  40         target.prefix = u"" # Make it hug the parentheses
  41         target.insert_child(0, lparen)
  42         target.append_child(RParen())