CODEWITHSUNDEEP
pythonjson
Peter Wang
Peter Wang

Reputation: 1838

Trouble updating json files

I have two json files. One of them is a dictionary which is a subset of the other.

json_file_1.json contains {'foo': 1, 'bar': 2, 'baz': 3}

json_file_2.json contains {'foo': 100, 'bar': 200}.

I want to create a final json file that has the following: {'foo': 100, 'bar': 200, 'baz': 3}

Here is what I tried so far:

with open('json_file_1.json') as f1:
    original_info = json.load(f1)
f1.close()

with open('json_file_2.json') as f2:
    updated_info = json.load(f2)
f2.close()

print original_info  # prints the correct dictionary
print updated_info   # prints the correct dictionary

final_info = original_info.update(updated_info)

print final_info  # prints None

with open('json_file_final.json', 'w+') as f_final:
    json.dump(final_info, f_final)

However, when I open the final json file, it only contains "Null". When I tried debugging it, I printed out original_info and updated_info, and they were each fine. I could call original_info.update(updated_info) and that would produce a dictionary that was properly updated. However, it just isn't working for some reason when it's all put together?

Any thoughts?

Thanks so much!

Upvotes: 0

Views: 36

Answers (1)

OneCricketeer
OneCricketeer

Reputation: 191728

dict.update updates a dictionary in-place and returns None.

You need to dump original_info

For reference, 

In [11]: d1 = {'foo': 1, 'bar': 2, 'baz': 3}

In [12]: d2 = {'foo': 100, 'bar': 200}

In [13]: d3 = d1.update(d2)

In [14]: d3

In [15]: print(d3)
None

In [16]: d1
Out[16]: {'bar': 200, 'baz': 3, 'foo': 100}

Upvotes: 2

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