django-prices: Django fields for the prices module

Installation

• pip install django-prices
• Add django_prices to your INSTALLED_APPS at settings.py

Features

Provides support for models:

from django.db import models
from django_prices.models import MoneyField, TaxedMoneyField


class Model(models.Model):
    currency = models.CharField(max_length=3, default="BTC")
    price_net_amount = models.DecimalField(max_digits=9, decimal_places=2, default="5")
    price_net = MoneyField(amount_field="price_net_amount", currency_field="currency")
    price_gross_amount = models.DecimalField(
        max_digits=9, decimal_places=2, default="5"
    )
    price_gross = MoneyField(
        amount_field="price_gross_amount", currency_field="currency"
    )
    price = TaxedMoneyField(
        net_amount_field="price_net_amount",
        gross_amount_field="price_gross_amount",
        currency="currency",
    )

And forms:

from django import forms

from django_prices.forms import MoneyField

AVAILABLE_CURRENCIES = ["BTC", "USD"]


class ProductForm(forms.Form):
    name = forms.CharField(label="Name")
    price_net = MoneyField(label="net", available_currencies=AVAILABLE_CURRENCIES)

And validators:

from django import forms
from prices.forms import Money

from django_prices.forms import MoneyField
from django_prices.validators import (
    MaxMoneyValidator, MinMoneyValidator, MoneyPrecisionValidator)


class DonateForm(forms.Form):
    donator_name = forms.CharField(label="Your name")
    donation = MoneyField(
        label="net",
        available_currencies=["BTC", "USD"],
        max_digits=9,
        decimal_places=2,
        validators=[
            MoneyPrecisionValidator(),
            MinMoneyValidator(Money(5, "USD")),
            MaxMoneyValidator(Money(500, "USD")),
        ],
    )

It also provides support for templates:

{% load prices %}

<p>Price: {{ foo.price.gross|amount }} ({{ foo.price.net|amount }} + {{ foo.price.tax|amount }} tax)</p>

You can also use HTML output from prices template tags, they will wrap currency symbol in a <span> element:

{% load prices %}

<p>Price: {{ foo.price.gross|amount:'html' }} ({{ foo.price.net|amount:'html' }} + {{ foo.price.tax|amount:'html' }} tax)</p>

It will be rendered as a following structure (for example with English locale):

<span class="currency">$</span>15.00

How to migrate to django-prices 2.0

Version 2.0 introduces major changes to how prices data is stored in models, enabling setting price's currency per model instance.

Steps to migrate:

1. In your forms:

   • remove the currency argument
   • add available_currencies with available choices.

   If the form specified MoneyFields in fields option, replace those with explicit declarations instead:

   AVAILABLE_CURRENCIES = [("BTC", "bitcoins"), ("USD", "US dollar")]
   
   class ModelForm(forms.ModelForm):
       class Meta:
           model = models.Model
           fields = []
   
       price_net = MoneyField(available_currencies=AVAILABLE_CURRENCIES)
   

2. In your models using MoneyField:

   • Replace all occurrences of the MoneyField class with DecimalField

   • Remove the currency argument from them

   • Change default from Money instance to value acceptable by Decimal field

     Example of code:

     price_net = MoneyField(
         "net", currency="BTC", default=Money("5", "BTC"), max_digits=9, decimal_places=2
     )
     

     Updated code:

     price_net = models.DecimalField("net", default="5", max_digits=9, decimal_places=2)
     

3. In your migration files:

   • Replace all occurrences of the MoneyField class with DecimalField

   • Remove the currency argument from them

   • Change default from Money instance to value acceptable by Decimal field

     field = django_prices.models.MoneyField(currency='BTC', decimal_places=2, default='5', max_digits=9, verbose_name='net')
     

     Updated code:

     field = models.DecimalField(decimal_places=2, default='5', max_digits=9, verbose_name='net')
     

4. Rename fields in models. Your old field will still store amount of money, so probably the best choice would be price_net_amount instead price_net.

5. All places which use Models and it's fields can prevent django app from even starting the code. Possible issues: code tries to access non existing fields. Exclude those fields for now from your ModelForms, Graphene types etc.

6. Run python manage.py makemigrations. Make sure to do this step before adding new MoneyFields to model! If not, django will generate delete/create migrations instead of rename.

7. Run python manage.py migrate.

8. Update django-prices.

9. Add models.CharField for currency and MoneyField to your models:

   currency = models.CharField(max_length=3, default="BTC")
   price_net_amount = models.DecimalField("net", default="5", max_digits=9, decimal_places=2)
   price_net = MoneyField(amount_field="price_net_amount", currency_field="currency")
   

10. Run python manage.py makemigrations and python manage.py migrate.

11. Change TaxedMoneyField declaration:

    price = TaxedMoneyField(
        net_amount_field="price_net_amount",
        gross_amount_field="price_gross_amount",
        currency="currency",
    )
    

12. Remember to address changes in previously edited ModelForms

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