Dumping multiple variables to disk in Json. One variable per line

Question

Say I want to dump multiple variables to disk with Json. They way I usually do this is by creating my variables as entries in a dictionary and then dumping the dictionary to disk:

with open(p_out, 'wb') as fp:
    json.dump(my_dictionary, fp)

This creates a json file where the dictionary is saved in a long line:

{"variable_1": something, "variable_2" something_else, ...}

which I don't like. I would prefer to have my variables dumped into the text file with one variable per line, e.g something along these lines:

{variable_1: something\n
 variable_2: something\n
 variable_3: something_else}

Is there a way to do this with Json in Python?

Assuming you had the dict {'variable_1': 'something'}, would you want the output file to contain "variable_1": "something" or variable_1: something. Without the quotes it is not JSON. — Andrew Clark
– Andrew Clark, Commented Dec 5, 2012 at 17:28

Martijn Pieters · Accepted Answer · 2012-12-05 17:25:52Z

3

Set the indent option to 0 or more:

with open(p_out, 'wb') as fp:
    json.dump(my_dictionary, fp, indent=0)

From the documentation:

If indent is a non-negative integer, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0, or negative, will only insert newlines. None (the default) selects the most compact representation.

Your example would be output as:

{
"variable_2": "something_else", 
"variable_1": "something"
}

answered Dec 5, 2012 at 17:25

Martijn Pieters

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2 Comments

Amelio Vazquez-Reina Over a year ago

Thanks, but this inserts new lines within each object as well (e.g. if variable_1 is a list, it will also insert new lines between every pair of items in the list). Is there a way to have new lines only between variables?

Martijn Pieters Over a year ago

@user273158: no, there isn't. You'd have to use .dumps() to dump to a string, then post-process before writing the result out to your file.

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