python 3 saving a dictionary

Question

I have looked at other questions on SO like this one but they are too techy for me to understand (only been learning a few days). I am making a phonebook and i am trying to save a dictionary like so,

numbers = {}
def save(a):
   x = open("phonebook.txt", "w")
   for l in a:
       x.write(l, a[l])
   x.close()

But i get error write() only takes 1 argument and obv im passing 2, so my question is how can i do this in a beginner freindly way and could you describe it in a non techy way. Thanks a lot.

Answer 1

It's better to use json module for dumping/loading dictionary to/from a file:

>>> import json
>>> numbers = {'1': 2, '3': 4, '5': 6}
>>> with open('numbers.txt', 'w') as f:
...     json.dump(numbers, f)
>>> with open('numbers.txt', 'r') as f:
...     print json.load(f)
... 
{u'1': 2, u'3': 4, u'5': 6}

Answer 2

While JSON is a good choice and is cross-language and supported by browsers, Python has its own serialization format called pickle that is much more flexible.

import pickle

data = {'Spam': 10, 'Eggs': 5, 'Bacon': 11}

with open('/tmp/data.pickle', 'w') as pfile:
    pickle.dump(data, pfile)

with open('/tmp/data.pickle', 'r') as pfile:
    read_data = pickle.load(pfile)

print(read_data)

Pickle is Python-specific, doesn't work with other languages, and be careful to never load pickle data from untrusted sources (such as over the web) as it's not considered "safe".

Pickle works for other data types too, including instances of your own classes.