Convert a python dict to a string and back

Question

I am writing a program that stores data in a dictionary object, but this data needs to be saved at some point during the program execution and loaded back into the dictionary object when the program is run again. How would I convert a dictionary object into a string that can be written to a file and loaded back into a dictionary object? This will hopefully support dictionaries containing dictionaries.

Answer 1

The json module is a good solution here. It has the advantages over pickle that it only produces plain text output, and is cross-platform and cross-version.

import json
json.dumps(dict)

Answer 2

If your dictionary isn't too big maybe str + eval can do the work:

dict1 = {'one':1, 'two':2, 'three': {'three.1': 3.1, 'three.2': 3.2 }}
str1 = str(dict1)

dict2 = eval(str1)

print(dict1 == dict2)

You can use ast.literal_eval instead of eval for additional security if the source is untrusted.

Answer 3

I use json:

import json

# convert to string
input_ = json.dumps({'id': id_ })
    
# load to dict
my_dict = json.loads(input_) 

Answer 4

Why not to use Python 3's inbuilt ast library's function literal_eval. It is better to use literal_eval instead of eval

import ast
str_of_dict = "{'key1': 'key1value', 'key2': 'key2value'}"
ast.literal_eval(str_of_dict)

will give output as actual Dictionary

{'key1': 'key1value', 'key2': 'key2value'}

And If you are asking to convert a Dictionary to a String then, How about using str() method of Python.

Suppose the dictionary is :

my_dict = {'key1': 'key1value', 'key2': 'key2value'}

And this will be done like this :

str(my_dict)

Will Print :

"{'key1': 'key1value', 'key2': 'key2value'}"

This is the easy as you like.

Answer 5

Use the pickle module to save it to disk and load later on.

Answer 6

Convert dictionary into JSON (string)

import json 

mydict = { "name" : "Don", 
          "surname" : "Mandol", 
          "age" : 43} 

result = json.dumps(mydict)

print(result[0:20])

will get you:

{"name": "Don", "sur

Convert string into dictionary

back_to_mydict = json.loads(result) 

Answer 7

In Chinese language you should do the following adjustments:

import codecs
fout = codecs.open("xxx.json", "w", "utf-8")
dict_to_json = json.dumps({'text':"中文"},ensure_ascii=False,indent=2)
fout.write(dict_to_json + '\n')

Answer 8

You may find the json.dumps() method needs help handling some object types.

Credit goes to the top answer of this post for the following:

import json
json.dumps(my_dictionary, indent=4, sort_keys=True, default=str)

Answer 9

I think you should consider using the shelve module which provides persistent file-backed dictionary-like objects. It's easy to use in place of a "real" dictionary because it almost transparently provides your program with something that can be used just like a dictionary, without the need to explicitly convert it to a string and then write to a file (or vice-versa).

The main difference is needing to initially open() it before first use and then close() it when you're done (and possibly sync()ing it, depending on the writeback option being used). Any "shelf" file objects create can contain regular dictionaries as values, allowing them to be logically nested.

Here's a trivial example:

import shelve

shelf = shelve.open('mydata')  # open for reading and writing, creating if nec
shelf.update({'one':1, 'two':2, 'three': {'three.1': 3.1, 'three.2': 3.2 }})
shelf.close()

shelf = shelve.open('mydata')
print shelf
shelf.close()

Output:

{'three': {'three.1': 3.1, 'three.2': 3.2}, 'two': 2, 'one': 1}

Answer 10

If you care about the speed use ujson (UltraJSON), which has the same API as json:

import ujson
ujson.dumps([{"key": "value"}, 81, True])
# '[{"key":"value"},81,true]'
ujson.loads("""[{"key": "value"}, 81, true]""")
# [{u'key': u'value'}, 81, True]

Answer 11

I use yaml for that if needs to be readable (neither JSON nor XML are that IMHO), or if reading is not necessary I use pickle.

Write

from pickle import dumps, loads
x = dict(a=1, b=2)
y = dict(c = x, z=3)
res = dumps(y)
open('/var/tmp/dump.txt', 'w').write(res)

Read back

from pickle import dumps, loads
rev = loads(open('/var/tmp/dump.txt').read())
print rev

Answer 12

I figured out the problem was not with my dict object it was the keys and values that were of RubyString type after loading it with RubyMarshl 'loads' method

So i did this:

dic_items = dict.items()
new_dict = {str(key): str(value) for key, value in dic_items}