module json
python 2.7.12

json.dump(..., indent=4, sort_keys=True) gives me:

{
    "size": {
        "total": 19106,X
        "code": 18614,X
        "data": 492
    },X
    "next_item": 10
}


The "X" mark extra trailing space characters which are needless.

This is documented behavior for Python 2 ( https://docs.python.org/2/library/json.html#basic-usage ):

>Note: Since the default item separator is ', ', the output might include trailing whitespace when indent is specified. You can use separators=(',', ': ') to avoid this.

and also:

If specified, separators should be an (item_separator, key_separator) tuple. By default, (', ', ': ') are used. To get the most compact JSON representation, you should specify (',', ':') to eliminate whitespace.

Python 3 gives a different guarantee (dynamically chosen default separators based on the value of indent), and it follows that contract.

Given it's clearly documented, easily worked around, and largely harmless, I see no strong argument for backporting the Python 3 behavior to the legacy codebase.

I agree with Josh's assessment. Sorry!

sorry, I missed that point in the docs.