cpython/Lib/lib2to3/fixes/fix_dict.py

# Copyright 2007 Google, Inc. All Rights Reserved.
# Licensed to PSF under a Contributor Agreement.

"""Fixer for dict methods.

d.keys() -> list(d.keys())
d.items() -> list(d.items())
d.values() -> list(d.values())

d.iterkeys() -> iter(d.keys())
d.iteritems() -> iter(d.items())
d.itervalues() -> iter(d.values())

d.viewkeys() -> d.keys()
d.viewitems() -> d.items()
d.viewvalues() -> d.values()

Except in certain very specific contexts: the iter() can be dropped
when the context is list(), sorted(), iter() or for...in; the list()
can be dropped when the context is list() or sorted() (but not iter()
or for...in!). Special contexts that apply to both: list(), sorted(), tuple()
set(), any(), all(), sum().

Note: iter(d.keys()) could be written as iter(d) but since the
original d.iterkeys() was also redundant we don't fix this.  And there
are (rare) contexts where it makes a difference (e.g. when passing it
as an argument to a function that introspects the argument).
"""

# Local imports
from .. import pytree
from .. import patcomp
from .. import fixer_base
from ..fixer_util import Name, Call, Dot
from .. import fixer_util


iter_exempt = fixer_util.consuming_calls | {"iter"}


class FixDict(fixer_base.BaseFix):
    BM_compatible = True

    PATTERN = """
    power< head=any+
         trailer< '.' method=('keys'|'items'|'values'|
                              'iterkeys'|'iteritems'|'itervalues'|
                              'viewkeys'|'viewitems'|'viewvalues') >
         parens=trailer< '(' ')' >
         tail=any*
    >
    """

    def transform(self, node, results):
        head = results["head"]
        method = results["method"][0] # Extract node for method name
        tail = results["tail"]
        syms = self.syms
        method_name = method.value
        isiter = method_name.startswith("iter")
        isview = method_name.startswith("view")
        if isiter or isview:
            method_name = method_name[4:]
        assert method_name in ("keys", "items", "values"), repr(method)
        head = [n.clone() for n in head]
        tail = [n.clone() for n in tail]
        special = not tail and self.in_special_context(node, isiter)
        args = head + [pytree.Node(syms.trailer,
                                   [Dot(),
                                    Name(method_name,
                                         prefix=method.prefix)]),
                       results["parens"].clone()]
        new = pytree.Node(syms.power, args)
        if not (special or isview):
            new.prefix = ""
            new = Call(Name("iter" if isiter else "list"), [new])
        if tail:
            new = pytree.Node(syms.power, [new] + tail)
        new.prefix = node.prefix
        return new

    P1 = "power< func=NAME trailer< '(' node=any ')' > any* >"
    p1 = patcomp.compile_pattern(P1)

    P2 = """for_stmt< 'for' any 'in' node=any ':' any* >
            | old_comp_for< 'for' any 'in' node=any any* >
         """
    p2 = patcomp.compile_pattern(P2)

    def in_special_context(self, node, isiter):
        if node.parent is None:
            return False
        results = {}
        if (node.parent.parent is not None and
               self.p1.match(node.parent.parent, results) and
               results["node"] is node):
            if isiter:
                # iter(d.iterkeys()) -> iter(d.keys()), etc.
                return results["func"].value in iter_exempt
            else:
                # list(d.keys()) -> list(d.keys()), etc.
                return results["func"].value in fixer_util.consuming_calls
        if not isiter:
            return False
        # for ... in d.iterkeys() -> for ... in d.keys(), etc.
        return self.p2.match(node.parent, results) and results["node"] is node