Django function to convert a dict to a Q object

readme.md

Dict to Q object

Django function to convert a dict with filters (allows lookups) to a Q object
Useful when receiving query params in the URL (API)

function dict_to_Q(filters_dict, valid_fields_operations=None, prefix='')

• filters_dict : dict
  • A dictionary containing the fields and respective filter lookups and values
  • Example: {'tsgte': '2020-10-12', 'tslte': '2021-10-12', ...}
• valid_fields_operations : dict | optional
  • Allowed fields and respective lookups in filters_dict
  • Default = None : doesn't verify validity (insecure)
  • Example: {'ts': ['gte', 'lte', 'exact'], 'hostname': []}
• prefix : str | optional
  • Specifies a model to add at the begining of every field in the returned Q object.
  • Defaults to ''.
  • Example:

    >>>dict_to_Q({'ts__gte': '2020-10-12'}, prefix='pc')
    <Q: (AND: ('pc__ts__gte', '2020-10-12'))>

Returns:

• django.db.models.Q : Q object with the filters of the dictionary

Raises:

• TypeError: Invalid field name
• TypeError: Invalid filter lookup for the field

Example:

>>> print(request.GET.dict())
{'ts__gte': ['2020-02-15'], 'ts__lte': ['2020-10-12']}
>>> print(ComputerRecordFilter.get_fields())
OrderedDict([('pc__hostname', ['exact', 'iexact', 'isnull', 'regex', 'iregex', 'contains', 'icontains', 'in', 'gt', 'gte', 'lt', 'lte', 'startswith', 'istartswith', 'endswith', 'iendswith', 'range']), ('ts', ['exact', 'iexact', 'isnull', 'regex', 'iregex', 'contains', 'icontains', 'in', 'gt', 'gte', 'lt', 'lte', 'startswith', 'istartswith', 'endswith', 'iendswith', 'range', 'date', 'year', 'iso_year', 'month', 'day', 'week', 'week_day', 'quarter', 'time', 'hour', 'minute', 'second'])])
>>> dict_to_Q(request.GET.dict(), ComputerRecordFilter.get_fields(), 'computerrecord')
 <Q: (AND: ('computerrecord__ts__gte', '2020-10-12'), ('computerrecord__ts__lte', '2021-02-15'))>

dict_to_Q.py

def dict_to_Q(filters_dict, valid_fields_operations=None, prefix=''):
    """
    Converts a dictionary to Q filter object
    Args:
        filters_dict (dict): 
            Must contain fields, filter lookups and values. 
            Example: {'ts__gte': '2020-10-12', ...}
        valid_fields_operations (dict, optional): 
            Mapping for valid field names and corresponding filter lookups. 
            Defaults to None : doesn't verify validity (insecure)
            Example: {'ts': ['gte', 'lte', 'exact'], ...}
        prefix (str, optional): 
            Specifies a model to add at the begining of every field. 
            Defaults to ''.
            Example: 
            >>> dict_to_Q({'ts__gte': '2020-10-12'}, prefix='pc')
            <Q: (AND: ('pc__ts__gte', '2020-10-12'))>

    Raises:
        TypeError: Invalid field name
        TypeError: Invalid filter lookup for the field

    Returns:
        Q: Q object with the filters of the dictionary
    """
    ret_dict = dict()
    if prefix != '':
        prefix += '__'

    for filter_field in filters_dict:
        filter_sep = filter_field.split('__')
        fname = filter_sep[0]
        lookup = filter_sep[1] if len(filter_sep) == 2 else 'exact'

        if valid_fields_operations:
            if fname not in valid_fields_operations:
                raise TypeError(f"Invalid field name: '{fname}'")
            if lookup not in valid_fields_operations.get(fname):
                raise TypeError(f"There is no valid operation '{lookup}' for the '{fname}' field")

        ret_dict[prefix + filter_field] = filters_dict.get(filter_field)

    return Q(**ret_dict)

Example:

>>> print(request.GET)
<QueryDict: {'ts__gte': ['2020-02-15'], 'ts__lte': ['2020-10-12']}>
>>> dict_to_Q(request.GET.dict(), ComputerRecordFilter.get_fields(), 'computerrecord')
 <Q: (AND: ('computerrecord__ts__gte', '2020-10-12'), ('computerrecord__ts__lte', '2021-02-15'))>