1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
# Copyright 2016 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Canonicalizing list comprehensions into for and if statements.
e.g.
result = [x * x for x in xs]
becomes
result = []
for x in xs:
elt = x * x
result.append(elt)
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import gast
from tensorflow.contrib.autograph.core import converter
from tensorflow.contrib.autograph.pyct import parser
from tensorflow.contrib.autograph.pyct import templates
class ListCompCanonicalizationTransformer(converter.Base):
"""NodeTransformer to canonicalize list comprehensions."""
def make_update_list_node(self, list_, elt):
return templates.replace('list_.append(elt)', list_=list_, elt=elt)[0]
def instantiate_list_node(self):
return parser.parse_str('[]').body[0].value
def visit_Assign(self, node):
if not isinstance(node.value, gast.ListComp):
return node
if len(node.targets) > 1:
raise ValueError('Only support single assignment.')
return self.canonicalize_listcomp(node.targets[0], node.value)
def canonicalize_listcomp(self, result_node, list_comp_node):
make_list = templates.replace(
'list_ = create_list',
list_=result_node,
create_list=self.instantiate_list_node())
loop_body = self.make_update_list_node(result_node, list_comp_node.elt)
for gen in reversed(list_comp_node.generators):
for gen_if in reversed(gen.ifs):
loop_body = templates.replace(
'if test: loop_body', test=gen_if, loop_body=loop_body)
loop_body = templates.replace(
'for target in iter_: loop_body',
iter_=gen.iter,
target=gen.target,
loop_body=loop_body)
return make_list + loop_body
def transform(node, ctx):
return ListCompCanonicalizationTransformer(ctx).visit(node)
|
