name : fix_unpacking.py 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" "))