diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index f30010f9..e7b8b1a4 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,23 +1,24 @@
 repos:
 -   repo: git://github.com/pre-commit/pre-commit-hooks
-    rev: v1.3.0
+    rev: v2.1.0
     hooks:
+    -   id: check-merge-conflict
     -   id: check-json
     -   id: check-yaml
     -   id: debug-statements
     -   id: end-of-file-fixer
         exclude: ^docs/.*$
-    -   id: trailing-whitespace
-        exclude: README.md
     -   id: pretty-format-json
         args:
         - --autofix
+    -   id: trailing-whitespace
+        exclude: README.md
 -   repo: https://github.com/asottile/pyupgrade
-    rev: v1.4.0
+    rev: v1.12.0
     hooks:
     -   id: pyupgrade
 -   repo: https://github.com/ambv/black
-    rev: 18.6b4
+    rev: 18.9b0
     hooks:
     - id: black
-      language_version: python3.6
+      language_version: python3
diff --git a/graphql/execution/utils.py b/graphql/execution/utils.py
index b1e7ff25..d4fe4f7a 100644
--- a/graphql/execution/utils.py
+++ b/graphql/execution/utils.py
@@ -121,11 +121,15 @@ def __init__(
         self.variable_values = variable_values
         self.errors = errors
         self.context_value = context_value
-        self.argument_values_cache = {}  # type: Dict[Tuple[GraphQLField, Field], Dict[str, Any]]
+        self.argument_values_cache = (
+            {}
+        )  # type: Dict[Tuple[GraphQLField, Field], Dict[str, Any]]
         self.executor = executor
         self.middleware = middleware
         self.allow_subscriptions = allow_subscriptions
-        self._subfields_cache = {}  # type: Dict[Tuple[GraphQLObjectType, Tuple[Field, ...]], DefaultOrderedDict]
+        self._subfields_cache = (
+            {}
+        )  # type: Dict[Tuple[GraphQLObjectType, Tuple[Field, ...]], DefaultOrderedDict]
 
     def get_field_resolver(self, field_resolver):
         # type: (Callable) -> Callable
diff --git a/graphql/language/lexer.py b/graphql/language/lexer.py
index a60bc6e2..45cd6683 100644
--- a/graphql/language/lexer.py
+++ b/graphql/language/lexer.py
@@ -245,7 +245,7 @@ def position_after_whitespace(body, start_position):
 
 def read_number(source, start, first_code):
     # type: (Source, int, Optional[int]) -> Token
-    """Reads a number token from the source file, either a float
+    r"""Reads a number token from the source file, either a float
     or an int depending on whether a decimal point appears.
 
     Int:   -?(0|[1-9][0-9]*)
diff --git a/graphql/utils/type_info.py b/graphql/utils/type_info.py
index 76433eb6..f3862f30 100644
--- a/graphql/utils/type_info.py
+++ b/graphql/utils/type_info.py
@@ -60,8 +60,12 @@ def __init__(self, schema, get_field_def_fn=get_field_def):
         # type: (GraphQLSchema, Callable) -> None
         self._schema = schema
         self._type_stack = []  # type: List[Optional[GraphQLType]]
-        self._parent_type_stack = []  # type: List[Union[GraphQLInterfaceType, GraphQLObjectType, None]]
-        self._input_type_stack = []  # type: List[Optional[Union[GraphQLInputObjectType, GraphQLNonNull, GraphQLList, GraphQLScalarType, None]]]
+        self._parent_type_stack = (
+            []
+        )  # type: List[Union[GraphQLInterfaceType, GraphQLObjectType, None]]
+        self._input_type_stack = (
+            []
+        )  # type: List[Optional[Union[GraphQLInputObjectType, GraphQLNonNull, GraphQLList, GraphQLScalarType, None]]]
         self._field_def_stack = []  # type: List[Optional[GraphQLField]]
         self._directive = None  # type: Optional[GraphQLDirective]
         self._argument = None  # type: Optional[GraphQLArgument]
diff --git a/graphql/validation/rules/overlapping_fields_can_be_merged.py b/graphql/validation/rules/overlapping_fields_can_be_merged.py
index 8506e2cd..08f40f1b 100644
--- a/graphql/validation/rules/overlapping_fields_can_be_merged.py
+++ b/graphql/validation/rules/overlapping_fields_can_be_merged.py
@@ -47,7 +47,9 @@ def __init__(self, context):
         # A cache for the "field map" and list of fragment names found in any given
         # selection set. Selection sets may be asked for this information multiple
         # times, so this improves the performance of this validator.
-        self._cached_fields_and_fragment_names = {}  # type: Dict[SelectionSet, Tuple[Dict[str, List[Tuple[Union[GraphQLInterfaceType, GraphQLObjectType, None], Field, GraphQLField]]], List[str]]]
+        self._cached_fields_and_fragment_names = (
+            {}
+        )  # type: Dict[SelectionSet, Tuple[Dict[str, List[Tuple[Union[GraphQLInterfaceType, GraphQLObjectType, None], Field, GraphQLField]]], List[str]]]
 
     def leave_SelectionSet(
         self,
diff --git a/graphql/validation/validation.py b/graphql/validation/validation.py
index ed647742..ed6c520b 100644
--- a/graphql/validation/validation.py
+++ b/graphql/validation/validation.py
@@ -86,9 +86,13 @@ def __init__(self, schema, ast, type_info):
         self._errors = []  # type: List[GraphQLError]
         self._fragments = None  # type: Optional[Dict[str, FragmentDefinition]]
         self._fragment_spreads = {}  # type: Dict[Node, List[FragmentSpread]]
-        self._recursively_referenced_fragments = {}  # type: Dict[OperationDefinition, List[FragmentSpread]]
+        self._recursively_referenced_fragments = (
+            {}
+        )  # type: Dict[OperationDefinition, List[FragmentSpread]]
         self._variable_usages = {}  # type: Dict[Node, List[VariableUsage]]
-        self._recursive_variable_usages = {}  # type: Dict[OperationDefinition, List[VariableUsage]]
+        self._recursive_variable_usages = (
+            {}
+        )  # type: Dict[OperationDefinition, List[VariableUsage]]
 
     def report_error(self, error):
         self._errors.append(error)