python json float with leading zeros

Question

How to use python (3.5) json standard library to print floats with trailing zeros?

import json
to_be_serialized = {'something': 0.020}
print(json.dumps(to_be_serialized))
{"something": 0.02}  # desired output: {"something": 0.020}

I tried this but unfortunately without desired result.

score 1 · Answer 1 · answered Dec 18 '17 at 09:02

1

Floats aren't designed to hold that kind of information. 0.020 and 0.02 are identical.

You can however manually set the number of decimals:

import json
test = 0.020
print(json.dumps({'test': '{:.3f}'.format(test)}))

will print

{"test": "0.020"}

Note that a) this is now a string and no longer a float and b) that the {:.3f} part specifically sets the number of decimals to three.

answered Dec 18 '17 at 09:02

orangeInk

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b) is ok for me, a) not :( – Martin Brisiak Dec 18 '17 at 14:25
What is it you're actually trying to achieve? Why do you need the trailing zeros? – orangeInk Dec 18 '17 at 15:00
those are just the requirements – Martin Brisiak Dec 19 '17 at 06:31

Martin Brisiak · Accepted Answer · 2017-12-19T11:56:48.713

1

In the end I was forced to use non-standard python library simplejson. (cause json package is not supporting decimals)

import simplejson as json
from decimal import Decimal

to_be_serialized = {'something': Decimal('0.020').quantize(Decimal('.0001'))}
print(json.dumps(to_be_serialized))

I was unable to find a way to do this with standard json library, but at least it's working.

edited Dec 19 '17 at 11:56

answered Dec 19 '17 at 08:59

Martin Brisiak

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python json float with leading zeros

2 Answers2