将python字符串转换为字典

Question

I have an excel document with a row, something like:

{MGY: {1: 85, 2: 15}}
{MGY: {1:85, 2:15}, MWH: {1:99, 2:1}, MDE: {1:60, 2:40}, MIN: {1:60, 2:40}}
{MGY: {1:85, 2:15}}
{MWH: {1:99, 2:1}}
{MGY: {1:85, 2:15}}

When I try to convert the row to a dictionary using, the following code:

Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> meta = {u'CODE': u'N03', u'FABRIC': u'Jersey', u'Colour mix': u'{MGY: {1: 85, 2: 15}}', u'WEIGHT G': 165, u'Main': u'3:100', u'WEIGHT OZ': 4}
>>> colour_mix = meta['Colour mix']
>>> colour_mix
u'{MGY: {1: 85, 2: 15}}'
>>> import ast
>>> melange_items = ast.literal_eval(colour_mix)

I get the following traceback:

Traceback (most recent call last):
  File "styles_fabric.py", line 194, in <module>
    styleMeta = fabric_composition(style)
  File "styles_fabric.py", line 185, in fabric_composition
    melange_items = ast.literal_eval(dd)
  File "/usr/lib/python2.7/ast.py", line 80, in literal_eval
    return _convert(node_or_string)
  File "/usr/lib/python2.7/ast.py", line 63, in _convert
    in zip(node.keys, node.values))
  File "/usr/lib/python2.7/ast.py", line 62, in <genexpr>
    return dict((_convert(k), _convert(v)) for k, v
  File "/usr/lib/python2.7/ast.py", line 79, in _convert
    raise ValueError('malformed string')
ValueError: malformed string

what is the correct way to extract, convert the strings in dictionaries?

Answer 1

I think you meant to wrap the key into quotes:

import ast
ast.literal_eval('{"MGY": {1: 85, 2: 15}}') # {'MGY': {1: 85, 2: 15}}

ast.literal_eval can parse string literals, but MGY itself doesn't mean anything to it.

Answer 2

I think you should use JSON instead of Python represantation to keep your data as string

>>> meta = {u'CODE': u'N03', u'FABRIC': u'Jersey', u'Colour mix': u'{MGY: {1: 85, 2: 15}}', u'WEIGHT G': 165, u'Main': u'3:100', u'WEIGHT OZ': 4}
>>> import json
>>> str = json.dumps(meta)
>>> str
'{"CODE": "N03", "FABRIC": "Jersey", "Colour mix": "{MGY: {1: 85, 2: 15}}", "WEIGHT G": 165, "Main": "3:100", "WEIGHT OZ": 4}'
>>> meta2 = json.loads(str)
>>> meta == meta2
True

JSON is designed for that purpose, so you have a better chance that authors of json package thought about all aspects of keeping data as strings. Authors of ast probably were thinking about source code.

Answer 3

Try to use Yaml for Python to deal with the un-stand json data, here is an example:

import yaml
import ast

meta = {u'CODE': u'N03', u'FABRIC': u'Jersey', u'Colour mix': u'{MGY: {1: 85, 2: 15}}', u'WEIGHT G': 165, u'Main': u'3:100', u'WEIGHT OZ': 4}

colour_mix = meta['Colour mix']
str_json_data = str(yaml.load(colour_mix))
print str_json_data
print ast.literal_eval(str_json_data)