DecimalField won't accept a float

Question

I have a model:

Model(models.Model)
    price = models.DecimalField(max_digits=10, decimal_places=2)

and I have a string:

new_price = "39.99"

When I try the following:

model_instance.price = float(new_price)
model_instance.save()

I get django.core.exceptions.ValidationError: {'price': ['Ensure that there are no more than 10 digits in total.']}

Why?

Answer 1

That has to do with Python's internal float representation's limitations . But you can use the string directly with a DecimalField :

model_instance.price = "39.99"
model_instance.save()

If you have dynamic input you can use decimal.Decimal directly to get the required precision:

from decimal import *

model_instance.price = Decimal(new_price).quantize(
    Decimal('0.01'), 
    rounding=ROUND_HALF_UP)

Answer 2

尝试使用decimal.Decimal代替float（）