Float operations can lead to a false fail of `multipleOf`

[lorinkoz]

Hi, much ❤️ to the library.

I found this validation problem when using multipleOf:

>>> from jsonschema import validate
>>> validate(instance=10.1, schema={"type":"number", "multipleOf":0.1})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/path/to/python/site-packages/jsonschema/validators.py", line 934, in validate
    raise error
jsonschema.exceptions.ValidationError: 10.1 is not a multiple of 0.1

Failed validating 'multipleOf' in schema:
    {'multipleOf': 0.1, 'type': 'number'}

On instance:
    10.1

When printing the cotient that results from this code:
https://github.com/Julian/jsonschema/blob/0ea12edea319580473bda7e26ef088ff3a0983c5/jsonschema/_validators.py#L169

The cotient is 100.99999999999999

Therefore, int(quotient) can't be quotient on https://github.com/Julian/jsonschema/blob/0ea12edea319580473bda7e26ef088ff3a0983c5/jsonschema/_validators.py#L171

What to do?

[Julian]

Hi there, thanks!

If you want fixed point precision (or generally non-float behavior), you should use decimal.Decimal when deserializing your JSON.

[lorinkoz]

Okay, thanks. I guess that's the solution, then. Keep up the good work!

[tdamsma]

As this is the first issue I stumbled upon, I'm adding these links for reference: #687, #185, #320, #247