Viewing file:  fix_unpacking.py (5.81 KB) -rw-r--r--
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u"""
Fixer for:
(a,)* *b (,c)* [,] = s
for (a,)* *b (,c)* [,] in d: ...
"""
from lib2to3 import fixer_base
from itertools import count
from lib2to3.fixer_util import (Assign, Comma, Call, Newline, Name,
Number, token, syms, Node, Leaf)
from libfuturize.fixer_util import indentation, suitify, commatize
# from libfuturize.fixer_util import Assign, Comma, Call, Newline, Name, Number, indentation, suitify, commatize, token, syms, Node, Leaf
def assignment_source(num_pre, num_post, LISTNAME, ITERNAME):
u"""
Accepts num_pre and num_post, which are counts of values
before and after the starg (not including the starg)
Returns a source fit for Assign() from fixer_util
"""
children = []
pre = unicode(num_pre)
post = unicode(num_post)
# This code builds the assignment source from lib2to3 tree primitives.
# It's not very readable, but it seems like the most correct way to do it.
if num_pre > 0:
pre_part = Node(syms.power, [Name(LISTNAME), Node(syms.trailer, [Leaf(token.LSQB, u"["), Node(syms.subscript, [Leaf(token.COLON, u":"), Number(pre)]), Leaf(token.RSQB, u"]")])])
children.append(pre_part)
children.append(Leaf(token.PLUS, u"+", prefix=u" "))
main_part = Node(syms.power, [Leaf(token.LSQB, u"[", prefix=u" "), Name(LISTNAME), Node(syms.trailer, [Leaf(token.LSQB, u"["), Node(syms.subscript, [Number(pre) if num_pre > 0 else Leaf(1, u""), Leaf(token.COLON, u":"), Node(syms.factor, [Leaf(token.MINUS, u"-"), Number(post)]) if num_post > 0 else Leaf(1, u"")]), Leaf(token.RSQB, u"]"), Leaf(token.RSQB, u"]")])])
children.append(main_part)
if num_post > 0:
children.append(Leaf(token.PLUS, u"+", prefix=u" "))
post_part = Node(syms.power, [Name(LISTNAME, prefix=u" "), Node(syms.trailer, [Leaf(token.LSQB, u"["), Node(syms.subscript, [Node(syms.factor, [Leaf(token.MINUS, u"-"), Number(post)]), Leaf(token.COLON, u":")]), Leaf(token.RSQB, u"]")])])
children.append(post_part)
source = Node(syms.arith_expr, children)
return source
class FixUnpacking(fixer_base.BaseFix):
PATTERN = u"""
expl=expr_stmt< testlist_star_expr<
pre=(any ',')*
star_expr< '*' name=NAME >
post=(',' any)* [','] > '=' source=any > |
impl=for_stmt< 'for' lst=exprlist<
pre=(any ',')*
star_expr< '*' name=NAME >
post=(',' any)* [','] > 'in' it=any ':' suite=any>"""
def fix_explicit_context(self, node, results):
pre, name, post, source = (results.get(n) for n in (u"pre", u"name", u"post", u"source"))
pre = [n.clone() for n in pre if n.type == token.NAME]
name.prefix = u" "
post = [n.clone() for n in post if n.type == token.NAME]
target = [n.clone() for n in commatize(pre + [name.clone()] + post)]
# to make the special-case fix for "*z, = ..." correct with the least
# amount of modification, make the left-side into a guaranteed tuple
target.append(Comma())
source.prefix = u""
setup_line = Assign(Name(self.LISTNAME), Call(Name(u"list"), [source.clone()]))
power_line = Assign(target, assignment_source(len(pre), len(post), self.LISTNAME, self.ITERNAME))
return setup_line, power_line
def fix_implicit_context(self, node, results):
u"""
Only example of the implicit context is
a for loop, so only fix that.
"""
pre, name, post, it = (results.get(n) for n in (u"pre", u"name", u"post", u"it"))
pre = [n.clone() for n in pre if n.type == token.NAME]
name.prefix = u" "
post = [n.clone() for n in post if n.type == token.NAME]
target = [n.clone() for n in commatize(pre + [name.clone()] + post)]
# to make the special-case fix for "*z, = ..." correct with the least
# amount of modification, make the left-side into a guaranteed tuple
target.append(Comma())
source = it.clone()
source.prefix = u""
setup_line = Assign(Name(self.LISTNAME), Call(Name(u"list"), [Name(self.ITERNAME)]))
power_line = Assign(target, assignment_source(len(pre), len(post), self.LISTNAME, self.ITERNAME))
return setup_line, power_line
def transform(self, node, results):
u"""
a,b,c,d,e,f,*g,h,i = range(100) changes to
_3to2list = list(range(100))
a,b,c,d,e,f,g,h,i, = _3to2list[:6] + [_3to2list[6:-2]] + _3to2list[-2:]
and
for a,b,*c,d,e in iter_of_iters: do_stuff changes to
for _3to2iter in iter_of_iters:
_3to2list = list(_3to2iter)
a,b,c,d,e, = _3to2list[:2] + [_3to2list[2:-2]] + _3to2list[-2:]
do_stuff
"""
self.LISTNAME = self.new_name(u"_3to2list")
self.ITERNAME = self.new_name(u"_3to2iter")
expl, impl = results.get(u"expl"), results.get(u"impl")
if expl is not None:
setup_line, power_line = self.fix_explicit_context(node, results)
setup_line.prefix = expl.prefix
power_line.prefix = indentation(expl.parent)
setup_line.append_child(Newline())
parent = node.parent
i = node.remove()
parent.insert_child(i, power_line)
parent.insert_child(i, setup_line)
elif impl is not None:
setup_line, power_line = self.fix_implicit_context(node, results)
suitify(node)
suite = [k for k in node.children if k.type == syms.suite][0]
setup_line.prefix = u""
power_line.prefix = suite.children[1].value
suite.children[2].prefix = indentation(suite.children[2])
suite.insert_child(2, Newline())
suite.insert_child(2, power_line)
suite.insert_child(2, Newline())
suite.insert_child(2, setup_line)
results.get(u"lst").replace(Name(self.ITERNAME, prefix=u" "))
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