Merge branch 'master' of github.com:MongoEngine/mongoengine into fix_complex_datetime_field_invalid_string_set

mongoengine/fields.py

@@ -5,14 +5,14 @@ import re
 import socket
 import time
 import uuid
+from io import BytesIO
 from operator import itemgetter
 
 from bson import Binary, DBRef, ObjectId, SON
+from bson.int64 import Int64
 import gridfs
 import pymongo
 from pymongo import ReturnDocument
-import six
-from six import iteritems
 
 try:
     import dateutil
@@ -21,11 +21,6 @@ except ImportError:
 else:
     import dateutil.parser
 
-try:
-    from bson.int64 import Int64
-except ImportError:
-    Int64 = long
-
 
 from mongoengine.base import (
     BaseDocument,
@@ -42,7 +37,6 @@ from mongoengine.connection import DEFAULT_CONNECTION_NAME, get_db
 from mongoengine.document import Document, EmbeddedDocument
 from mongoengine.errors import DoesNotExist, InvalidQueryError, ValidationError
 from mongoengine.mongodb_support import MONGODB_36, get_mongodb_version
-from mongoengine.python_support import StringIO
 from mongoengine.queryset import DO_NOTHING
 from mongoengine.queryset.base import BaseQuerySet
 from mongoengine.queryset.transform import STRING_OPERATORS
@@ -53,11 +47,6 @@ except ImportError:
     Image = None
     ImageOps = None
 
-if six.PY3:
-    # Useless as long as 2to3 gets executed
-    # as it turns `long` into `int` blindly
-    long = int
-
 
 __all__ = (
     "StringField",
@@ -114,10 +103,10 @@ class StringField(BaseField):
         self.regex = re.compile(regex) if regex else None
         self.max_length = max_length
         self.min_length = min_length
-        super(StringField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
-        if isinstance(value, six.text_type):
+        if isinstance(value, str):
             return value
         try:
             value = value.decode("utf-8")
@@ -126,7 +115,7 @@ class StringField(BaseField):
         return value
 
     def validate(self, value):
-        if not isinstance(value, six.string_types):
+        if not isinstance(value, str):
             self.error("StringField only accepts string values")
 
         if self.max_length is not None and len(value) > self.max_length:
@@ -142,7 +131,7 @@ class StringField(BaseField):
         return None
 
     def prepare_query_value(self, op, value):
-        if not isinstance(op, six.string_types):
+        if not isinstance(op, str):
             return value
 
         if op in STRING_OPERATORS:
@@ -162,7 +151,7 @@ class StringField(BaseField):
             # escape unsafe characters which could lead to a re.error
             value = re.escape(value)
             value = re.compile(regex % value, flags)
-        return super(StringField, self).prepare_query_value(op, value)
+        return super().prepare_query_value(op, value)
 
 
 class URLField(StringField):
@@ -186,17 +175,17 @@ class URLField(StringField):
     def __init__(self, url_regex=None, schemes=None, **kwargs):
         self.url_regex = url_regex or self._URL_REGEX
         self.schemes = schemes or self._URL_SCHEMES
-        super(URLField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def validate(self, value):
         # Check first if the scheme is valid
         scheme = value.split("://")[0].lower()
         if scheme not in self.schemes:
-            self.error(u"Invalid scheme {} in URL: {}".format(scheme, value))
+            self.error("Invalid scheme {} in URL: {}".format(scheme, value))
 
         # Then check full URL
         if not self.url_regex.match(value):
-            self.error(u"Invalid URL: {}".format(value))
+            self.error("Invalid URL: {}".format(value))
 
 
 class EmailField(StringField):
@@ -214,7 +203,7 @@ class EmailField(StringField):
     )
 
     UTF8_USER_REGEX = LazyRegexCompiler(
-        six.u(
+        (
             # RFC 6531 Section 3.3 extends `atext` (used by dot-atom) to
             # include `UTF8-non-ascii`.
             r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z\u0080-\U0010FFFF]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z\u0080-\U0010FFFF]+)*\Z"
@@ -229,7 +218,7 @@ class EmailField(StringField):
         re.IGNORECASE,
     )
 
-    error_msg = u"Invalid email address: %s"
+    error_msg = "Invalid email address: %s"
 
     def __init__(
         self,
@@ -253,7 +242,7 @@ class EmailField(StringField):
         self.domain_whitelist = domain_whitelist or []
         self.allow_utf8_user = allow_utf8_user
         self.allow_ip_domain = allow_ip_domain
-        super(EmailField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def validate_user_part(self, user_part):
         """Validate the user part of the email address. Return True if
@@ -280,13 +269,13 @@ class EmailField(StringField):
                 try:
                     socket.inet_pton(addr_family, domain_part[1:-1])
                     return True
-                except (socket.error, UnicodeEncodeError):
+                except (OSError, UnicodeEncodeError):
                     pass
 
         return False
 
     def validate(self, value):
-        super(EmailField, self).validate(value)
+        super().validate(value)
 
         if "@" not in value:
             self.error(self.error_msg % value)
@@ -303,12 +292,16 @@ class EmailField(StringField):
                 domain_part = domain_part.encode("idna").decode("ascii")
             except UnicodeError:
                 self.error(
-                    "%s %s" % (self.error_msg % value, "(domain failed IDN encoding)")
+                    "{} {}".format(
+                        self.error_msg % value, "(domain failed IDN encoding)"
+                    )
                 )
             else:
                 if not self.validate_domain_part(domain_part):
                     self.error(
-                        "%s %s" % (self.error_msg % value, "(domain validation failed)")
+                        "{} {}".format(
+                            self.error_msg % value, "(domain validation failed)"
+                        )
                     )
 
 
@@ -317,7 +310,7 @@ class IntField(BaseField):
 
     def __init__(self, min_value=None, max_value=None, **kwargs):
         self.min_value, self.max_value = min_value, max_value
-        super(IntField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
         try:
@@ -342,19 +335,19 @@ class IntField(BaseField):
         if value is None:
             return value
 
-        return super(IntField, self).prepare_query_value(op, int(value))
+        return super().prepare_query_value(op, int(value))
 
 
 class LongField(BaseField):
-    """64-bit integer field."""
+    """64-bit integer field. (Equivalent to IntField since the support to Python2 was dropped)"""
 
     def __init__(self, min_value=None, max_value=None, **kwargs):
         self.min_value, self.max_value = min_value, max_value
-        super(LongField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
         try:
-            value = long(value)
+            value = int(value)
         except (TypeError, ValueError):
             pass
         return value
@@ -364,7 +357,7 @@ class LongField(BaseField):
 
     def validate(self, value):
         try:
-            value = long(value)
+            value = int(value)
         except (TypeError, ValueError):
             self.error("%s could not be converted to long" % value)
 
@@ -378,7 +371,7 @@ class LongField(BaseField):
         if value is None:
             return value
 
-        return super(LongField, self).prepare_query_value(op, long(value))
+        return super().prepare_query_value(op, int(value))
 
 
 class FloatField(BaseField):
@@ -386,7 +379,7 @@ class FloatField(BaseField):
 
     def __init__(self, min_value=None, max_value=None, **kwargs):
         self.min_value, self.max_value = min_value, max_value
-        super(FloatField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
         try:
@@ -396,7 +389,7 @@ class FloatField(BaseField):
         return value
 
     def validate(self, value):
-        if isinstance(value, six.integer_types):
+        if isinstance(value, int):
             try:
                 value = float(value)
             except OverflowError:
@@ -415,7 +408,7 @@ class FloatField(BaseField):
         if value is None:
             return value
 
-        return super(FloatField, self).prepare_query_value(op, float(value))
+        return super().prepare_query_value(op, float(value))
 
 
 class DecimalField(BaseField):
@@ -462,7 +455,7 @@ class DecimalField(BaseField):
         self.precision = precision
         self.rounding = rounding
 
-        super(DecimalField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
         if value is None:
@@ -481,13 +474,13 @@ class DecimalField(BaseField):
         if value is None:
             return value
         if self.force_string:
-            return six.text_type(self.to_python(value))
+            return str(self.to_python(value))
         return float(self.to_python(value))
 
     def validate(self, value):
         if not isinstance(value, decimal.Decimal):
-            if not isinstance(value, six.string_types):
-                value = six.text_type(value)
+            if not isinstance(value, str):
+                value = str(value)
             try:
                 value = decimal.Decimal(value)
             except (TypeError, ValueError, decimal.InvalidOperation) as exc:
@@ -500,7 +493,7 @@ class DecimalField(BaseField):
             self.error("Decimal value is too large")
 
     def prepare_query_value(self, op, value):
-        return super(DecimalField, self).prepare_query_value(op, self.to_mongo(value))
+        return super().prepare_query_value(op, self.to_mongo(value))
 
 
 class BooleanField(BaseField):
@@ -540,7 +533,7 @@ class DateTimeField(BaseField):
     def validate(self, value):
         new_value = self.to_mongo(value)
         if not isinstance(new_value, (datetime.datetime, datetime.date)):
-            self.error(u'cannot parse date "%s"' % value)
+            self.error('cannot parse date "%s"' % value)
 
     def to_mongo(self, value):
         if value is None:
@@ -552,7 +545,7 @@ class DateTimeField(BaseField):
         if callable(value):
             return value()
 
-        if not isinstance(value, six.string_types):
+        if not isinstance(value, str):
             return None
 
         return self._parse_datetime(value)
@@ -597,19 +590,19 @@ class DateTimeField(BaseField):
                     return None
 
     def prepare_query_value(self, op, value):
-        return super(DateTimeField, self).prepare_query_value(op, self.to_mongo(value))
+        return super().prepare_query_value(op, self.to_mongo(value))
 
 
 class DateField(DateTimeField):
     def to_mongo(self, value):
-        value = super(DateField, self).to_mongo(value)
+        value = super().to_mongo(value)
         # drop hours, minutes, seconds
         if isinstance(value, datetime.datetime):
             value = datetime.datetime(value.year, value.month, value.day)
         return value
 
     def to_python(self, value):
-        value = super(DateField, self).to_python(value)
+        value = super().to_python(value)
         # convert datetime to date
         if isinstance(value, datetime.datetime):
             value = datetime.date(value.year, value.month, value.day)
@@ -643,7 +636,7 @@ class ComplexDateTimeField(StringField):
         """
         self.separator = separator
         self.format = separator.join(["%Y", "%m", "%d", "%H", "%M", "%S", "%f"])
-        super(ComplexDateTimeField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def _convert_from_datetime(self, val):
         """
@@ -674,14 +667,14 @@ class ComplexDateTimeField(StringField):
         if instance is None:
             return self
 
-        data = super(ComplexDateTimeField, self).__get__(instance, owner)
+        data = super().__get__(instance, owner)
 
         if isinstance(data, datetime.datetime) or data is None:
             return data
         return self._convert_from_string(data)
 
     def __set__(self, instance, value):
-        super(ComplexDateTimeField, self).__set__(instance, value)
+        super().__set__(instance, value)
         value = instance._data[self.name]
         if value is not None:
             if isinstance(value, datetime.datetime):
@@ -706,9 +699,7 @@ class ComplexDateTimeField(StringField):
         return self._convert_from_datetime(value)
 
     def prepare_query_value(self, op, value):
-        return super(ComplexDateTimeField, self).prepare_query_value(
-            op, self._convert_from_datetime(value)
-        )
+        return super().prepare_query_value(op, self._convert_from_datetime(value))
 
 
 class EmbeddedDocumentField(BaseField):
@@ -719,7 +710,7 @@ class EmbeddedDocumentField(BaseField):
     def __init__(self, document_type, **kwargs):
         # XXX ValidationError raised outside of the "validate" method.
         if not (
-            isinstance(document_type, six.string_types)
+            isinstance(document_type, str)
             or issubclass(document_type, EmbeddedDocument)
         ):
             self.error(
@@ -728,11 +719,11 @@ class EmbeddedDocumentField(BaseField):
             )
 
         self.document_type_obj = document_type
-        super(EmbeddedDocumentField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     @property
     def document_type(self):
-        if isinstance(self.document_type_obj, six.string_types):
+        if isinstance(self.document_type_obj, str):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
                 resolved_document_type = self.owner_document
             else:
@@ -789,7 +780,7 @@ class EmbeddedDocumentField(BaseField):
                     "Querying the embedded document '%s' failed, due to an invalid query value"
                     % (self.document_type._class_name,)
                 )
-        super(EmbeddedDocumentField, self).prepare_query_value(op, value)
+        super().prepare_query_value(op, value)
         return self.to_mongo(value)
 
 
@@ -805,9 +796,7 @@ class GenericEmbeddedDocumentField(BaseField):
     """
 
     def prepare_query_value(self, op, value):
-        return super(GenericEmbeddedDocumentField, self).prepare_query_value(
-            op, self.to_mongo(value)
-        )
+        return super().prepare_query_value(op, self.to_mongo(value))
 
     def to_python(self, value):
         if isinstance(value, dict):
@@ -858,7 +847,7 @@ class DynamicField(BaseField):
         """Convert a Python type to a MongoDB compatible type.
         """
 
-        if isinstance(value, six.string_types):
+        if isinstance(value, str):
             return value
 
         if hasattr(value, "to_mongo"):
@@ -880,12 +869,12 @@ class DynamicField(BaseField):
             value = {k: v for k, v in enumerate(value)}
 
         data = {}
-        for k, v in iteritems(value):
+        for k, v in value.items():
             data[k] = self.to_mongo(v, use_db_field, fields)
 
         value = data
         if is_list:  # Convert back to a list
-            value = [v for k, v in sorted(iteritems(data), key=itemgetter(0))]
+            value = [v for k, v in sorted(data.items(), key=itemgetter(0))]
         return value
 
     def to_python(self, value):
@@ -895,15 +884,15 @@ class DynamicField(BaseField):
                 value = doc_cls._get_db().dereference(value["_ref"])
             return doc_cls._from_son(value)
 
-        return super(DynamicField, self).to_python(value)
+        return super().to_python(value)
 
     def lookup_member(self, member_name):
         return member_name
 
     def prepare_query_value(self, op, value):
-        if isinstance(value, six.string_types):
+        if isinstance(value, str):
             return StringField().prepare_query_value(op, value)
-        return super(DynamicField, self).prepare_query_value(op, self.to_mongo(value))
+        return super().prepare_query_value(op, self.to_mongo(value))
 
     def validate(self, value, clean=True):
         if hasattr(value, "validate"):
@@ -924,7 +913,7 @@ class ListField(ComplexBaseField):
         self.field = field
         self.max_length = max_length
         kwargs.setdefault("default", lambda: [])
-        super(ListField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def __get__(self, instance, owner):
         if instance is None:
@@ -938,7 +927,7 @@ class ListField(ComplexBaseField):
             and value
         ):
             instance._data[self.name] = [self.field.build_lazyref(x) for x in value]
-        return super(ListField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def validate(self, value):
         """Make sure that a list of valid fields is being used."""
@@ -952,7 +941,7 @@ class ListField(ComplexBaseField):
         if self.max_length is not None and len(value) > self.max_length:
             self.error("List is too long")
 
-        super(ListField, self).validate(value)
+        super().validate(value)
 
     def prepare_query_value(self, op, value):
         # Validate that the `set` operator doesn't contain more items than `max_length`.
@@ -966,14 +955,14 @@ class ListField(ComplexBaseField):
             if (
                 op in ("set", "unset", None)
                 and hasattr(value, "__iter__")
-                and not isinstance(value, six.string_types)
+                and not isinstance(value, str)
                 and not isinstance(value, BaseDocument)
             ):
                 return [self.field.prepare_query_value(op, v) for v in value]
 
             return self.field.prepare_query_value(op, value)
 
-        return super(ListField, self).prepare_query_value(op, value)
+        return super().prepare_query_value(op, value)
 
 
 class EmbeddedDocumentListField(ListField):
@@ -994,9 +983,7 @@ class EmbeddedDocumentListField(ListField):
         :param kwargs: Keyword arguments passed directly into the parent
          :class:`~mongoengine.ListField`.
         """
-        super(EmbeddedDocumentListField, self).__init__(
-            field=EmbeddedDocumentField(document_type), **kwargs
-        )
+        super().__init__(field=EmbeddedDocumentField(document_type), **kwargs)
 
 
 class SortedListField(ListField):
@@ -1022,10 +1009,10 @@ class SortedListField(ListField):
             self._ordering = kwargs.pop("ordering")
         if "reverse" in kwargs.keys():
             self._order_reverse = kwargs.pop("reverse")
-        super(SortedListField, self).__init__(field, **kwargs)
+        super().__init__(field, **kwargs)
 
     def to_mongo(self, value, use_db_field=True, fields=None):
-        value = super(SortedListField, self).to_mongo(value, use_db_field, fields)
+        value = super().to_mongo(value, use_db_field, fields)
         if self._ordering is not None:
             return sorted(
                 value, key=itemgetter(self._ordering), reverse=self._order_reverse
@@ -1038,9 +1025,7 @@ def key_not_string(d):
     dictionary is not a string.
     """
     for k, v in d.items():
-        if not isinstance(k, six.string_types) or (
-            isinstance(v, dict) and key_not_string(v)
-        ):
+        if not isinstance(k, str) or (isinstance(v, dict) and key_not_string(v)):
             return True
 
 
@@ -1080,7 +1065,7 @@ class DictField(ComplexBaseField):
         self._auto_dereference = False
 
         kwargs.setdefault("default", lambda: {})
-        super(DictField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def validate(self, value):
         """Make sure that a list of valid fields is being used."""
@@ -1100,7 +1085,7 @@ class DictField(ComplexBaseField):
             self.error(
                 'Invalid dictionary key name - keys may not startswith "$" characters'
             )
-        super(DictField, self).validate(value)
+        super().validate(value)
 
     def lookup_member(self, member_name):
         return DictField(db_field=member_name)
@@ -1117,7 +1102,7 @@ class DictField(ComplexBaseField):
             "iexact",
         ]
 
-        if op in match_operators and isinstance(value, six.string_types):
+        if op in match_operators and isinstance(value, str):
             return StringField().prepare_query_value(op, value)
 
         if hasattr(
@@ -1129,7 +1114,7 @@ class DictField(ComplexBaseField):
                 }
             return self.field.prepare_query_value(op, value)
 
-        return super(DictField, self).prepare_query_value(op, value)
+        return super().prepare_query_value(op, value)
 
 
 class MapField(DictField):
@@ -1144,7 +1129,7 @@ class MapField(DictField):
         # XXX ValidationError raised outside of the "validate" method.
         if not isinstance(field, BaseField):
             self.error("Argument to MapField constructor must be a valid field")
-        super(MapField, self).__init__(field=field, *args, **kwargs)
+        super().__init__(field=field, *args, **kwargs)
 
 
 class ReferenceField(BaseField):
@@ -1204,7 +1189,7 @@ class ReferenceField(BaseField):
             :class:`~pymongo.dbref.DBRef`, regardless of the value of `dbref`.
         """
         # XXX ValidationError raised outside of the "validate" method.
-        if not isinstance(document_type, six.string_types) and not issubclass(
+        if not isinstance(document_type, str) and not issubclass(
             document_type, Document
         ):
             self.error(
@@ -1215,11 +1200,11 @@ class ReferenceField(BaseField):
         self.dbref = dbref
         self.document_type_obj = document_type
         self.reverse_delete_rule = reverse_delete_rule
-        super(ReferenceField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     @property
     def document_type(self):
-        if isinstance(self.document_type_obj, six.string_types):
+        if isinstance(self.document_type_obj, str):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
                 self.document_type_obj = self.owner_document
             else:
@@ -1248,7 +1233,7 @@ class ReferenceField(BaseField):
             else:
                 instance._data[self.name] = cls._from_son(dereferenced)
 
-        return super(ReferenceField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def to_mongo(self, document):
         if isinstance(document, DBRef):
@@ -1299,7 +1284,7 @@ class ReferenceField(BaseField):
     def prepare_query_value(self, op, value):
         if value is None:
             return None
-        super(ReferenceField, self).prepare_query_value(op, value)
+        super().prepare_query_value(op, value)
         return self.to_mongo(value)
 
     def validate(self, value):
@@ -1335,7 +1320,7 @@ class CachedReferenceField(BaseField):
             fields = []
 
         # XXX ValidationError raised outside of the "validate" method.
-        if not isinstance(document_type, six.string_types) and not issubclass(
+        if not isinstance(document_type, str) and not issubclass(
             document_type, Document
         ):
             self.error(
@@ -1346,7 +1331,7 @@ class CachedReferenceField(BaseField):
         self.auto_sync = auto_sync
         self.document_type_obj = document_type
         self.fields = fields
-        super(CachedReferenceField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def start_listener(self):
         from mongoengine import signals
@@ -1358,7 +1343,7 @@ class CachedReferenceField(BaseField):
             return None
 
         update_kwargs = {
-            "set__%s__%s" % (self.name, key): val
+            "set__{}__{}".format(self.name, key): val
             for key, val in document._delta()[0].items()
             if key in self.fields
         }
@@ -1380,7 +1365,7 @@ class CachedReferenceField(BaseField):
 
     @property
     def document_type(self):
-        if isinstance(self.document_type_obj, six.string_types):
+        if isinstance(self.document_type_obj, str):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
                 self.document_type_obj = self.owner_document
             else:
@@ -1404,7 +1389,7 @@ class CachedReferenceField(BaseField):
             else:
                 instance._data[self.name] = self.document_type._from_son(dereferenced)
 
-        return super(CachedReferenceField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def to_mongo(self, document, use_db_field=True, fields=None):
         id_field_name = self.document_type._meta["id_field"]
@@ -1503,12 +1488,12 @@ class GenericReferenceField(BaseField):
 
     def __init__(self, *args, **kwargs):
         choices = kwargs.pop("choices", None)
-        super(GenericReferenceField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
         self.choices = []
         # Keep the choices as a list of allowed Document class names
         if choices:
             for choice in choices:
-                if isinstance(choice, six.string_types):
+                if isinstance(choice, str):
                     self.choices.append(choice)
                 elif isinstance(choice, type) and issubclass(choice, Document):
                     self.choices.append(choice._class_name)
@@ -1517,7 +1502,7 @@ class GenericReferenceField(BaseField):
                     # method.
                     self.error(
                         "Invalid choices provided: must be a list of"
-                        "Document subclasses and/or six.string_typess"
+                        "Document subclasses and/or str"
                     )
 
     def _validate_choices(self, value):
@@ -1527,7 +1512,7 @@ class GenericReferenceField(BaseField):
             value = value.get("_cls")
         elif isinstance(value, Document):
             value = value._class_name
-        super(GenericReferenceField, self)._validate_choices(value)
+        super()._validate_choices(value)
 
     def __get__(self, instance, owner):
         if instance is None:
@@ -1543,7 +1528,7 @@ class GenericReferenceField(BaseField):
             else:
                 instance._data[self.name] = dereferenced
 
-        return super(GenericReferenceField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def validate(self, value):
         if not isinstance(value, (Document, DBRef, dict, SON)):
@@ -1607,22 +1592,22 @@ class BinaryField(BaseField):
 
     def __init__(self, max_bytes=None, **kwargs):
         self.max_bytes = max_bytes
-        super(BinaryField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def __set__(self, instance, value):
         """Handle bytearrays in python 3.1"""
-        if six.PY3 and isinstance(value, bytearray):
-            value = six.binary_type(value)
-        return super(BinaryField, self).__set__(instance, value)
+        if isinstance(value, bytearray):
+            value = bytes(value)
+        return super().__set__(instance, value)
 
     def to_mongo(self, value):
         return Binary(value)
 
     def validate(self, value):
-        if not isinstance(value, (six.binary_type, Binary)):
+        if not isinstance(value, (bytes, Binary)):
             self.error(
                 "BinaryField only accepts instances of "
-                "(%s, %s, Binary)" % (six.binary_type.__name__, Binary.__name__)
+                "(%s, %s, Binary)" % (bytes.__name__, Binary.__name__)
             )
 
         if self.max_bytes is not None and len(value) > self.max_bytes:
@@ -1631,14 +1616,14 @@ class BinaryField(BaseField):
     def prepare_query_value(self, op, value):
         if value is None:
             return value
-        return super(BinaryField, self).prepare_query_value(op, self.to_mongo(value))
+        return super().prepare_query_value(op, self.to_mongo(value))
 
 
 class GridFSError(Exception):
     pass
 
 
-class GridFSProxy(object):
+class GridFSProxy:
     """Proxy object to handle writing and reading of files to and from GridFS
 
     .. versionadded:: 0.4
@@ -1688,8 +1673,6 @@ class GridFSProxy(object):
     def __bool__(self):
         return bool(self.grid_id)
 
-    __nonzero__ = __bool__  # For Py2 support
-
     def __getstate__(self):
         self_dict = self.__dict__
         self_dict["_fs"] = None
@@ -1704,12 +1687,12 @@ class GridFSProxy(object):
         return self.__copy__()
 
     def __repr__(self):
-        return "<%s: %s>" % (self.__class__.__name__, self.grid_id)
+        return "<{}: {}>".format(self.__class__.__name__, self.grid_id)
 
     def __str__(self):
         gridout = self.get()
         filename = getattr(gridout, "filename") if gridout else "<no file>"
-        return "<%s: %s (%s)>" % (self.__class__.__name__, filename, self.grid_id)
+        return "<{}: {} ({})>".format(self.__class__.__name__, filename, self.grid_id)
 
     def __eq__(self, other):
         if isinstance(other, GridFSProxy):
@@ -1820,7 +1803,7 @@ class FileField(BaseField):
     def __init__(
         self, db_alias=DEFAULT_CONNECTION_NAME, collection_name="fs", **kwargs
     ):
-        super(FileField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
         self.collection_name = collection_name
         self.db_alias = db_alias
 
@@ -1843,7 +1826,7 @@ class FileField(BaseField):
         key = self.name
         if (
             hasattr(value, "read") and not isinstance(value, GridFSProxy)
-        ) or isinstance(value, (six.binary_type, six.string_types)):
+        ) or isinstance(value, (bytes, str)):
             # using "FileField() = file/string" notation
             grid_file = instance._data.get(self.name)
             # If a file already exists, delete it
@@ -1961,11 +1944,11 @@ class ImageGridFsProxy(GridFSProxy):
 
         w, h = img.size
 
-        io = StringIO()
+        io = BytesIO()
         img.save(io, img_format, progressive=progressive)
         io.seek(0)
 
-        return super(ImageGridFsProxy, self).put(
+        return super().put(
             io, width=w, height=h, format=img_format, thumbnail_id=thumb_id, **kwargs
         )
 
@@ -1975,12 +1958,12 @@ class ImageGridFsProxy(GridFSProxy):
         if out and out.thumbnail_id:
             self.fs.delete(out.thumbnail_id)
 
-        return super(ImageGridFsProxy, self).delete()
+        return super().delete()
 
     def _put_thumbnail(self, thumbnail, format, progressive, **kwargs):
         w, h = thumbnail.size
 
-        io = StringIO()
+        io = BytesIO()
         thumbnail.save(io, format, progressive=progressive)
         io.seek(0)
 
@@ -2050,16 +2033,11 @@ class ImageField(FileField):
         for att_name, att in extra_args.items():
             value = None
             if isinstance(att, (tuple, list)):
-                if six.PY3:
-                    value = dict(
-                        itertools.zip_longest(params_size, att, fillvalue=None)
-                    )
-                else:
-                    value = dict(map(None, params_size, att))
+                value = dict(itertools.zip_longest(params_size, att, fillvalue=None))
 
             setattr(self, att_name, value)
 
-        super(ImageField, self).__init__(collection_name=collection_name, **kwargs)
+        super().__init__(collection_name=collection_name, **kwargs)
 
 
 class SequenceField(BaseField):
@@ -2111,14 +2089,14 @@ class SequenceField(BaseField):
         self.value_decorator = (
             value_decorator if callable(value_decorator) else self.VALUE_DECORATOR
         )
-        super(SequenceField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def generate(self):
         """
         Generate and Increment the counter
         """
         sequence_name = self.get_sequence_name()
-        sequence_id = "%s.%s" % (sequence_name, self.name)
+        sequence_id = "{}.{}".format(sequence_name, self.name)
         collection = get_db(alias=self.db_alias)[self.collection_name]
 
         counter = collection.find_one_and_update(
@@ -2132,7 +2110,7 @@ class SequenceField(BaseField):
     def set_next_value(self, value):
         """Helper method to set the next sequence value"""
         sequence_name = self.get_sequence_name()
-        sequence_id = "%s.%s" % (sequence_name, self.name)
+        sequence_id = "{}.{}".format(sequence_name, self.name)
         collection = get_db(alias=self.db_alias)[self.collection_name]
         counter = collection.find_one_and_update(
             filter={"_id": sequence_id},
@@ -2149,7 +2127,7 @@ class SequenceField(BaseField):
         as it is only fixed on set.
         """
         sequence_name = self.get_sequence_name()
-        sequence_id = "%s.%s" % (sequence_name, self.name)
+        sequence_id = "{}.{}".format(sequence_name, self.name)
         collection = get_db(alias=self.db_alias)[self.collection_name]
         data = collection.find_one({"_id": sequence_id})
 
@@ -2172,7 +2150,7 @@ class SequenceField(BaseField):
             )
 
     def __get__(self, instance, owner):
-        value = super(SequenceField, self).__get__(instance, owner)
+        value = super().__get__(instance, owner)
         if value is None and instance._initialised:
             value = self.generate()
             instance._data[self.name] = value
@@ -2185,7 +2163,7 @@ class SequenceField(BaseField):
         if value is None and instance._initialised:
             value = self.generate()
 
-        return super(SequenceField, self).__set__(instance, value)
+        return super().__set__(instance, value)
 
     def prepare_query_value(self, op, value):
         """
@@ -2219,14 +2197,14 @@ class UUIDField(BaseField):
         .. versionchanged:: 0.6.19
         """
         self._binary = binary
-        super(UUIDField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     def to_python(self, value):
         if not self._binary:
             original_value = value
             try:
-                if not isinstance(value, six.string_types):
-                    value = six.text_type(value)
+                if not isinstance(value, str):
+                    value = str(value)
                 return uuid.UUID(value)
             except (ValueError, TypeError, AttributeError):
                 return original_value
@@ -2234,8 +2212,8 @@ class UUIDField(BaseField):
 
     def to_mongo(self, value):
         if not self._binary:
-            return six.text_type(value)
-        elif isinstance(value, six.string_types):
+            return str(value)
+        elif isinstance(value, str):
             return uuid.UUID(value)
         return value
 
@@ -2246,7 +2224,7 @@ class UUIDField(BaseField):
 
     def validate(self, value):
         if not isinstance(value, uuid.UUID):
-            if not isinstance(value, six.string_types):
+            if not isinstance(value, str):
                 value = str(value)
             try:
                 uuid.UUID(value)
@@ -2445,7 +2423,7 @@ class LazyReferenceField(BaseField):
           document. Note this only work getting field (not setting or deleting).
         """
         # XXX ValidationError raised outside of the "validate" method.
-        if not isinstance(document_type, six.string_types) and not issubclass(
+        if not isinstance(document_type, str) and not issubclass(
             document_type, Document
         ):
             self.error(
@@ -2457,11 +2435,11 @@ class LazyReferenceField(BaseField):
         self.passthrough = passthrough
         self.document_type_obj = document_type
         self.reverse_delete_rule = reverse_delete_rule
-        super(LazyReferenceField, self).__init__(**kwargs)
+        super().__init__(**kwargs)
 
     @property
     def document_type(self):
-        if isinstance(self.document_type_obj, six.string_types):
+        if isinstance(self.document_type_obj, str):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
                 self.document_type_obj = self.owner_document
             else:
@@ -2500,7 +2478,7 @@ class LazyReferenceField(BaseField):
         if value:
             instance._data[self.name] = value
 
-        return super(LazyReferenceField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def to_mongo(self, value):
         if isinstance(value, LazyReference):
@@ -2564,7 +2542,7 @@ class LazyReferenceField(BaseField):
     def prepare_query_value(self, op, value):
         if value is None:
             return None
-        super(LazyReferenceField, self).prepare_query_value(op, value)
+        super().prepare_query_value(op, value)
         return self.to_mongo(value)
 
     def lookup_member(self, member_name):
@@ -2591,12 +2569,12 @@ class GenericLazyReferenceField(GenericReferenceField):
 
     def __init__(self, *args, **kwargs):
         self.passthrough = kwargs.pop("passthrough", False)
-        super(GenericLazyReferenceField, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def _validate_choices(self, value):
         if isinstance(value, LazyReference):
             value = value.document_type._class_name
-        super(GenericLazyReferenceField, self)._validate_choices(value)
+        super()._validate_choices(value)
 
     def build_lazyref(self, value):
         if isinstance(value, LazyReference):
@@ -2625,7 +2603,7 @@ class GenericLazyReferenceField(GenericReferenceField):
         if value:
             instance._data[self.name] = value
 
-        return super(GenericLazyReferenceField, self).__get__(instance, owner)
+        return super().__get__(instance, owner)
 
     def validate(self, value):
         if isinstance(value, LazyReference) and value.pk is None:
@@ -2633,7 +2611,7 @@ class GenericLazyReferenceField(GenericReferenceField):
                 "You can only reference documents once they have been"
                 " saved to the database"
             )
-        return super(GenericLazyReferenceField, self).validate(value)
+        return super().validate(value)
 
     def to_mongo(self, document):
         if document is None:
@@ -2652,4 +2630,4 @@ class GenericLazyReferenceField(GenericReferenceField):
                 )
             )
         else:
-            return super(GenericLazyReferenceField, self).to_mongo(document)
+            return super().to_mongo(document)