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[英]How to save escape sequences to a file in python without double backslashes?
[英]How get back a proper json that was stored with fileInfo without the escape sequences?
我无法检索存储在 Maya 的fileInfo
的确切JSON 字符串转储 ( json.dumps
)。
>>> import pymel.core as pc
>>> json.dumps({'foo': 123})
'{"foo": 123}'
>>> pc.fileInfo['foo'] = json.dumps({'foo': 123})
>>> pc.fileInfo['foo']
u'{\\"foo\\": 123}'
>>> json.loads(pc.fileInfo['foo']) # this produces an error because of the escape sequence
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "c:\Program Files\Autodesk\Maya2011\bin\python26.zip\json\__init__.py", line 307, in loads
File "c:\Program Files\Autodesk\Maya2011\bin\python26.zip\json\decoder.py", line 319, in decode
File "c:\Program Files\Autodesk\Maya2011\bin\python26.zip\json\decoder.py", line 336, in raw_decode
File "c:\Program Files\Autodesk\Maya2011\bin\python26.zip\json\scanner.py", line 55, in iterscan
File "c:\Program Files\Autodesk\Maya2011\bin\python26.zip\json\decoder.py", line 171, in JSONObject
ValueError: Expecting property name: line 1 column 1 (char 1)
问题是当 Maya 存储一个值时,它确保它被正确转义。 但是当这个字符串被检索到它的json.loads
格式json.loads
。 我怎样才能解决这个问题?
我基本上要寻找的是在保存值的同时对 MEL 引入的转义序列进行转义的东西? 到目前为止,我还没有找到任何可以做到这一点的东西。
MEL 与 C 有很多相似之处,因此转义序列与 C 的转义序列大部分相同,如上所示。
确保文件完整地进出文件的最佳方法是在进出时对其进行 base64 编码并在出路时对其进行解码。 Maya 不会为您执行此操作,而且正如您所见,它提供的转义很奇怪。
这是我使用的; 它使用 yaml,但您应该可以毫无问题地交换 json。 我已经用它来按照你想要的方式持久化 yaml 数据。
'''
mayaPersist - namespace for functions related to storing data in fileInfo objects inside the current Maya file
I've tested this (a little) with as many as 100,000 integers - it works but it's slooow at that size
< 1000 values seems imperceptible
'''
import yaml
import base64
from maya.cmds import fileInfo
import itertools
def save(key, value):
'''
save the specified value as a base64 encoded yaml dunp at key 'key'
'''
encoded =encode(value)
fileInfo(key, encoded)
def load(key):
'''
return the value stored at 'key', or None if the value can't be found
@note it is possible to store a 'None' in the value, so this doesn't prove that the key does not exist !
'''
answer = fileInfo(key, q=True)
if not answer:
return None
return decode(answer[0])
def exists(key):
'''
returns true if the specified key exists
'''
answer = fileInfo(key, q=True)
return len(answer) != 0
def ls():
'''
a generator that returns all of the key-value pairs in this file's fileInfo
@note: these are not decoded, because they contain a mix of native stirngs and b64 values
'''
all_values = fileInfo(q=True)
keys = itertools.islice(all_values, 0, None, 2)
values = itertools.islice(all_values, 1, None, 2)
return itertools.izip(keys, values)
def delete(key):
'''
remove the key and any data stored with it from this file
'''
fileInfo(rm=key)
def decode(value):
'''
convert a base64'ed yaml object back into a maya object
if the object is not encoded (eg, one of the default string values) return it untouched
'''
try:
val = base64.b64decode(value)
return yaml.load(val)
except TypeError:
return value
def encode (value):
'''
return the supplied value encoded into base64-packed YAML dump
'''
return base64.b64encode(yaml.dump(value))
@theodox 的答案可能是正确的。 但是如果你知道 json 字符串将被转义。 您可以简单地取回字符串的原始未转义版本。
mystring.decode('unicode_escape')
所以在上述情况下,反序列化存储信息的正确方法是:
json.loads(pc.fileInfo['foo'].decode('unicode_escape'))
不过它看起来有点难看,所以你可以把它放在一个函数中。
def safe_json_loads(str):
return json.loads(str.decode('unicode_escape'))
data = safe_json_loads(pc.fileInfo['foo'])
干杯,
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