How to write a dictionary into an existing file?

dictionary, python, python-3.3

Solution

You can use `json` module to read and write data structures in JSON format (in other words serialize to JSON and deserialize from JSON). For example:

import json

# load from file:
with open('/path/to/my_file.json', 'r') as f:
    try:
        data = json.load(f)
    # if the file is empty the ValueError will be thrown
    except ValueError:
        data = {}

# save to file:
with open('/path/to/my_file.json', 'w') as f:
    data['new_key'] = [1, 2, 3]
    json.dump(data, f)

Problem

Let's say I have a dictionary and I want to write it into an existing file. How can I do so without losing anything that could potentially already exist in the file? What I was thinking of is doing the following: ``` def write_report(r, filename): input_filename=open(filename, "a") input_filename.close() for (k,v) in r.items(): input_filename.write(k,v) return filename ``` what I want to make sure is that the filename correctly contains the dictionary.

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