Writing a dictionary to a text file?

I have a dictionary and am trying to write it to a file.

exDict = {1:1, 2:2, 3:3}
with open('file.txt', 'r') as file:
    file.write(exDict)

I then have the error

file.write(exDict)
TypeError: must be str, not dict

So I fixed that error but another error came

exDict = {111:111, 222:222}
with open('file.txt', 'r') as file:
    file.write(str(exDict))

The error:

file.write(str(exDict))
io.UnsupportedOperation: not writable

I have no idea what to do as I am still a beginner at python. If anyone knows how to resolve the issue, please provide an answer.

NOTE: I am using python 3, not python 2

Solution 1:

First of all you are opening file in read mode and trying to write into it. Consult - IO modes python

Secondly, you can only write a string to a file. If you want to write a dictionary object, you either need to convert it into string or serialize it.

import json

# as requested in comment
exDict = {'exDict': exDict}

with open('file.txt', 'w') as file:
     file.write(json.dumps(exDict)) # use `json.loads` to do the reverse

In case of serialization

import cPickle as pickle

with open('file.txt', 'w') as file:
     file.write(pickle.dumps(exDict)) # use `pickle.loads` to do the reverse

For python 3.x pickle package import would be different

import _pickle as pickle

Solution 2:

I do it like this in python 3:

with open('myfile.txt', 'w') as f:
    print(mydictionary, file=f)

Solution 3:

fout = "/your/outfile/here.txt"
fo = open(fout, "w")

for k, v in yourDictionary.items():
    fo.write(str(k) + ' >>> '+ str(v) + '\n\n')

fo.close()

Solution 4:

The probelm with your first code block was that you were opening the file as 'r' even though you wanted to write to it using 'w'

with open('/Users/your/path/foo','w') as data:
    data.write(str(dictionary))

Solution 5:

If you want a dictionary you can import from a file by name, and also that adds entries that are nicely sorted, and contains strings you want to preserve, you can try this:

data = {'A': 'a', 'B': 'b', }

with open('file.py','w') as file:
    file.write("dictionary_name = { \n")
    for k in sorted (data.keys()):
        file.write("'%s':'%s', \n" % (k, data[k]))
    file.write("}")

Then to import:

from file import dictionary_name