[英]ValueError: malformed node or string with ast.literal_eval() when adding a Keras layer
I want to build a Keras Model evaluating strings. 我想建立一个评估字符串的Keras模型。 If I do the following:
如果我执行以下操作:
from keras.models import Sequential
from keras.layers import Dense
model = Sequential()
model.add(Dense(units=10, input_shape=(10,), activation='softmax'))
It works fine. 它工作正常。 And I can see the
model.summary()
. 我可以看到
model.summary()
。
But, when I add the layer with ast.literal_eval()
但是,当我用
ast.literal_eval()
添加图层时
from keras.models import Sequential
from keras.layers import Dense
import ast
model = Sequential()
code = "model.add( Dense( input_shape=(10,), units=10, activation='softmax' ) )"
ast.literal_eval(code)
It throws me the next ValueError
: 它抛出了下一个
ValueError
:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3.5/ast.py", line 84, in literal_eval
return _convert(node_or_string)
File "/usr/lib/python3.5/ast.py", line 83, in _convert
raise ValueError('malformed node or string: ' + repr(node))
ValueError: malformed node or string: <_ast.Call object at 0x7efc40c90e10>
If I use eval
instead of ast.literal_eval
it works too. 如果我使用
eval
而不是ast.literal_eval
它也可以。
I'm using python3.5. 我正在使用python3.5。
A big mistake: literal_eval
only works for literals . 一个大错误:
literal_eval
仅适用于文字 。 In this case, I have a Call . 在这种情况下,我有一个电话 。
The function literal_eval
first parse the string. 函数
literal_eval
首先解析字符串。
From /usr/lib/python3.5/ast.py: lines 38-46 来自/usr/lib/python3.5/ast.py:行38-46
def literal_eval(node_or_string):
"""
Safely evaluate an expression node or a string containing a Python
expression. The string or node provided may only consist of the following
Python literal structures: strings, bytes, numbers, tuples, lists, dicts,
sets, booleans, and None.
"""
if isinstance(node_or_string, str):
node_or_string = parse(node_or_string, mode='eval')
At this point, node_or_string
is an instance of Expression
. 此时,
node_or_string
是Expression
的实例。 Then, literal_eval
get the body. 然后,
literal_eval
获取正文。
From /usr/lib/python3.5/ast.py: lines 47-48 来自/usr/lib/python3.5/ast.py:行47-48
if isinstance(node_or_string, Expression):
node_or_string = node_or_string.body
And finally, literal_eval
checks the type of the body ( node_or_string
). 最后,
literal_eval
检查正文的类型( node_or_string
)。
From /usr/lib/python3.5/ast.py: lines 49-84 来自/usr/lib/python3.5/ast.py:行49-84
def _convert(node):
if isinstance(node, (Str, Bytes)):
return node.s
elif isinstance(node, Num):
return node.n
elif isinstance(node, Tuple):
return tuple(map(_convert, node.elts))
elif isinstance(node, List):
return list(map(_convert, node.elts))
elif isinstance(node, Set):
return set(map(_convert, node.elts))
elif isinstance(node, Dict):
return dict((_convert(k), _convert(v)) for k, v
in zip(node.keys, node.values))
elif isinstance(node, NameConstant):
return node.value
elif isinstance(node, UnaryOp) and \
isinstance(node.op, (UAdd, USub)) and \
isinstance(node.operand, (Num, UnaryOp, BinOp)):
operand = _convert(node.operand)
if isinstance(node.op, UAdd):
return + operand
else:
return - operand
elif isinstance(node, BinOp) and \
isinstance(node.op, (Add, Sub)) and \
isinstance(node.right, (Num, UnaryOp, BinOp)) and \
isinstance(node.left, (Num, UnaryOp, BinOp)):
left = _convert(node.left)
right = _convert(node.right)
if isinstance(node.op, Add):
return left + right
else:
return left - right
raise ValueError('malformed node or string: ' + repr(node))
return _convert(node_or_string)
If the initial code was ast.literal_eval('1+1')
(for example), now node_or_string
would be an instance of BinOp
. 如果初始代码是
ast.literal_eval('1+1')
(例如), node_or_string
现在将是BinOp
的实例。 But in the case of: 但在以下情况下:
code = "model.add( Dense( input_shape=(10,), units=10, activation='softmax' ) )"
ast.literal_eval(code)
The body will be an instance of Call
, which does not appear among the valid types of the function. 正文将是
Call
一个实例,它不会出现在函数的有效类型中。
Eg: 例如:
import ast
code_nocall = "1+1"
node = ast.parse(code_nocall, mode='eval')
body = node.body
print(type(body)) # Returns <class '_ast.BinOp'>
code_call = "print('hello')"
node = ast.parse(code_call, mode='eval')
body = node.body
print(type(body)) # Returns <class '_ast.Call'>
The best solution I have found so far, to not use eval
directly, is to perform the process manually. 到目前为止,我发现的最佳解决方案是不直接使用
eval
,而是手动执行该过程。 With this function: 有了这个功能:
import ast
def eval_code(code):
parsed = ast.parse(code, mode='eval')
fixed = ast.fix_missing_locations(parsed)
compiled = compile(fixed, '<string>', 'eval')
eval(compiled)
Now it works: 它现在有效:
eval_code("print('hello world')")
from keras.models import Sequential
from keras.layers import Dense
model = Sequential()
code = "model.add( Dense( input_shape=(10,), units=10, activation='softmax' ) )"
eval_code(code)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.