Custom MethodFilter for django-filter

gistfile1.py

from django import forms
from django_filters import filters


filters.LOOKUP_TYPES = [
    ('', '---------'),
    ('exact', 'Is equal to'),
    ('not_exact', 'Is not equal to'),
    ('lt', 'Lesser than'),
    ('gt', 'Greater than'),
    ('gte', 'Greater than or equal to'),
    ('lte', 'Lesser than or equal to'),
    ('startswith', 'Starts with'),
    ('endswith', 'Ends with'),
    ('contains', 'Contains'),
    ('not_contains', 'Does not contain'),
]


class MethodFilter(filters.MethodFilter):
    def __init__(self, *args, **kwargs):
        self.field_class = kwargs.pop('field_class', forms.Field)

        kwargs.update({
            'lookup_type': None
        })

        super(MethodFilter, self).__init__(*args, **kwargs)

    def filter(self, queryset, value):
        lookup_type = value.lookup_type
        lookup_value = value.value

        if lookup_value in ([], (), {}, None, ''):
            return queryset

        parent = getattr(self, 'parent', None)
        parent_filter_method = getattr(parent, self.parent_action, None)

        if parent_filter_method is not None:
            return parent_filter_method(queryset, value)

        if lookup_type.startswith('not_'):
            method = queryset.exclude
        else:
            method = queryset.filter

        if lookup_type.startswith('not_'):
            lookup = lookup_type.replace('not_', '')

        return method(**{
            '{}__{}'.format(self.name, lookup): lookup_value
        })

usage.py

from django import forms

import django_filters
from ..utils.filters import MethodFilter, filter_by_method
from .models import Redemption


STATE_CHOICES = [('', '---------')] + \
    Redemption._meta.get_field_by_name('state')[0].choices


class RedemptionFilter(django_filters.FilterSet):
    user__email = MethodFilter(
        field_class=forms.CharField
    )

    date_created = MethodFilter(
        field_class=forms.DateField
    )

    amount = MethodFilter(
        field_class=forms.DecimalField,
        action='filter_amount'
    )

    state = MethodFilter(
        field_class=forms.ChoiceField,
        choices=STATE_CHOICES
    )

    class Meta:
        model = Redemption
        fields = [
            'user__email', 'amount', 'date_created', 'state'
        ]

    def filter_amount(self, queryset, value):
        return filter_by_method(queryset, value, 'amount')