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@Svenito Svenito/dictionaryfilter.py Secret
Last active Mar 24, 2020

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from rest_framework import filters
import json
from django.db.models import Q, F
import operator
from functools import reduce, partial
OP_MAP = {
"eq": "exact",
"gt": "gt",
"lt": "lt",
"gte": "gte",
"lte": "lte",
"in": "in",
"neq": "exact",
"startswith": "startswith",
"istartswith": "istartswith",
"endswith": "endswith",
"iendswith": "iendswith",
"contains": "contains",
"icontains": "icontains"
}
def create_q(filt):
"""
Parse a single filter into a Django Q expression. The OP_MAP
maps the operand from the query to the Django equivalent
"""
keyword = "{}__{}".format(filt["name"], OP_MAP[filt["op"]])
q_filter_parms = {}
filter_value = filt["val"]
if isinstance(filter_value, str) and filter_value.startswith("self."):
filter_value = F(filt["val"].split(".")[-1])
q_filter_parms[keyword] = filter_value
if filt["op"] == "neq":
return ~Q(**q_filter_parms)
else:
return Q(**q_filter_parms)
def parse_filter(user_filter, negate=False):
"""
Parse out a filter dictionary into a Q object
"""
if (
"or" not in user_filter
and "and" not in user_filter
and "not" not in user_filter
):
q_term = create_q(user_filter)
if negate:
return ~q_term
else:
return q_term
# process all the filters after the join operands by mapping
# them onto the pares_filter. Then use reduce to apply the
# operand to all the filters to join them
if "and" in user_filter:
mapped = map(parse_filter, user_filter.get("and"))
out_q = reduce(operator.and_, mapped)
return out_q
if "or" in user_filter:
mapped = map(parse_filter, user_filter.get("or"))
out_q = reduce(operator.or_, mapped)
return out_q
if "not" in user_filter:
# Partial to pass negate parm into map
invert = partial(parse_filter, negate=True)
mapped = map(invert, user_filter.get("not"))
out_q = reduce(operator.__invert__, mapped)
return out_q
class DictionaryFilter(filters.BaseFilterBackend):
"""
Get the filter expression and process the filters to return
a filtered queryset. If `filter` keyword missing return
unfiltered queryset
"""
def filter_queryset(self, request, queryset, view):
results = queryset
try:
filters = json.loads(request.query_params["filter"])
filt = parse_filter(filters)
results = queryset.filter(filt)
except KeyError:
pass
try:
sort = request.query_params["sort"]
results = results.order_by(sort)
except KeyError:
pass
return results
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