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.
This question is related to
python
json
dictionary
serialization
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
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.
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]
I use json
:
import json
# convert to string
input = json.dumps({'id': id })
# load to dict
my_dict = json.loads(input)
If in Chinses
import codecs
fout = codecs.open("xxx.json", "w", "utf-8")
dict_to_json = json.dumps({'text':"??"},ensure_ascii=False,indent=2)
fout.write(dict_to_json + '\n')
Use the pickle
module to save it to disk and load later on.
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.
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}
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)
Source: Stackoverflow.com