diff --git a/src/validr/__init__.py b/src/validr/__init__.py
index b0c4ef7..026732f 100644
--- a/src/validr/__init__.py
+++ b/src/validr/__init__.py
@@ -1,9 +1,18 @@
 """A simple, fast, extensible python library for data validation."""
-from .exception import Invalid, ModelInvalid, SchemaError, ValidrError, mark_index, mark_key
+from .model import ImmutableInstanceError, asdict, fields, modelclass
+from .schema import Builder, Compiler, Schema, T
 from .validator import (
-    create_re_validator, create_enum_validator, builtin_validators, validator)
-from .schema import Schema, Compiler, T, Builder
-from .model import modelclass, fields, asdict, ImmutableInstanceError
+    Invalid,
+    ModelInvalid,
+    SchemaError,
+    ValidrError,
+    builtin_validators,
+    create_enum_validator,
+    create_re_validator,
+)
+from .validator import py_mark_index as mark_index
+from .validator import py_mark_key as mark_key
+from .validator import validator
 
 __all__ = (
     'ValidrError', 'Invalid', 'ModelInvalid', 'SchemaError',
diff --git a/src/validr/_exception_c.pyx b/src/validr/_exception_c.pyx
deleted file mode 100644
index e2ae48d..0000000
--- a/src/validr/_exception_c.pyx
+++ /dev/null
@@ -1,176 +0,0 @@
-_NOT_SET = object()
-
-
-cdef _shorten(str text, int length):
-    if len(text) > length:
-        return text[:length] + '..'
-    return text
-
-
-cdef _format_value(value):
-    if isinstance(value, str):
-        return repr(_shorten(value, 75))
-    else:
-        return _shorten(str(value), 75)
-
-
-cdef _format_error(args, str position, str value_clause=None):
-    cdef str msg = str(args[0]) if args else 'invalid'
-    if position:
-        msg = '%s: %s' % (position, msg)
-    if value_clause:
-        msg = '%s, %s' % (msg, value_clause)
-    return msg
-
-
-class ValidrError(ValueError):
-    """Base exception of validr"""
-
-    def __init__(self, *args, value=_NOT_SET, **kwargs):
-        super().__init__(*args, **kwargs)
-        self._value = value
-        # marks item: (is_key, index_or_key)
-        self.marks = []
-
-    def mark_index(self, int index=-1):
-        self.marks.append((False, index))
-        return self
-
-    def mark_key(self, str key):
-        self.marks.append((True, key))
-        return self
-
-    @property
-    def has_value(self):
-        """Check has value set"""
-        return self._value is not _NOT_SET
-
-    def set_value(self, value):
-        """Set value if not set"""
-        if self._value is _NOT_SET:
-            self._value = value
-
-    @property
-    def value(self):
-        """The invalid value"""
-        if self._value is _NOT_SET:
-            return None
-        return self._value
-
-    @property
-    def field(self):
-        """First level index or key, usually it's the field"""
-        if not self.marks:
-            return None
-        __, index_or_key = self.marks[-1]
-        return index_or_key
-
-    @property
-    def position(self):
-        """A string which represent the position of invalid.
-
-        For example:
-
-            {
-                "tags": ["ok", "invalid"],  # tags[1]
-                "user": {
-                    "name": "invalid",      # user.name
-                    "age": 500              # user.age
-                }
-            }
-        """
-        cdef str text = ''
-        cdef bint is_key
-        for is_key, index_or_key in reversed(self.marks):
-            if is_key:
-                text = '%s.%s' % (text, index_or_key)
-            else:
-                if index_or_key == -1:
-                    text = '%s[]' % text
-                else:
-                    text = '%s[%d]' % (text, index_or_key)
-        if text and text[0] == '.':
-            text = text[1:]
-        return text
-
-    @property
-    def message(self):
-        """Error message"""
-        if self.args:
-            return self.args[0]
-        else:
-            return None
-
-    def __str__(self):
-        return _format_error(self.args, self.position)
-
-
-class Invalid(ValidrError):
-    """Data invalid"""
-    def __str__(self):
-        cdef str value_clause = None
-        if self.has_value:
-            value_clause = 'value=%s' % _format_value(self.value)
-        return _format_error(self.args, self.position, value_clause)
-
-
-class ModelInvalid(Invalid):
-    """Model data invalid"""
-    def __init__(self, errors):
-        if not errors:
-            raise ValueError('errors is required')
-        self.errors = errors
-        message = errors[0].message or 'invalid'
-        message += ' ...total {} errors'.format(len(errors))
-        super().__init__(message)
-
-    def __str__(self):
-        error_line_s = []
-        for ex in self.errors:
-            error_line_s.append('{} is {}'.format(ex.position, ex.message))
-        return '; '.join(error_line_s)
-
-
-class SchemaError(ValidrError):
-    """Schema error"""
-    def __str__(self):
-        cdef str value_clause = None
-        if self.has_value:
-            value_clause = 'schema=%s' % self.value.repr(prefix=False, desc=False)
-        return _format_error(self.args, self.position, value_clause)
-
-
-cdef class _mark_index:
-    """Add current index to Invalid/SchemaError"""
-
-    cdef int index
-
-    def __init__(self, index=-1):
-        """index = -1 means the position is uncertainty"""
-        self.index = index
-
-    def __enter__(self):
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        if exc_type is not None and issubclass(exc_type, ValidrError):
-            exc_val.mark_index(self.index)
-
-class mark_index(_mark_index): pass
-
-cdef class _mark_key:
-    """Add current key to Invalid/SchemaError"""
-
-    cdef str key
-
-    def __init__(self, key):
-        self.key = key
-
-    def __enter__(self):
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        if exc_type is not None and issubclass(exc_type, ValidrError):
-            exc_val.mark_key(self.key)
-
-class mark_key(_mark_key): pass
diff --git a/src/validr/_validator_c.pyx b/src/validr/_validator_c.pyx
index 809aa10..5666267 100644
--- a/src/validr/_validator_c.pyx
+++ b/src/validr/_validator_c.pyx
@@ -9,12 +9,190 @@ from copy import copy
 from functools import partial
 from urllib.parse import urlparse, urlunparse
 
-from .exception import Invalid, SchemaError, mark_key, mark_index
 from ._vendor import durationpy
 from ._vendor.email_validator import validate_email, EmailNotValidError
 from ._vendor.fqdn import FQDN
 
 
+_NOT_SET = object()
+
+
+cdef _shorten(str text, int length):
+    if len(text) > length:
+        return text[:length] + '..'
+    return text
+
+
+cdef _format_value(value):
+    if isinstance(value, str):
+        return repr(_shorten(value, 75))
+    else:
+        return _shorten(str(value), 75)
+
+
+cdef _format_error(args, str position, str value_clause=None):
+    cdef str msg = str(args[0]) if args else 'invalid'
+    if position:
+        msg = '%s: %s' % (position, msg)
+    if value_clause:
+        msg = '%s, %s' % (msg, value_clause)
+    return msg
+
+
+class ValidrError(ValueError):
+    """Base exception of validr"""
+
+    def __init__(self, *args, value=_NOT_SET, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._value = value
+        # marks item: (is_key, index_or_key)
+        self.marks = []
+
+    def mark_index(self, int index=-1):
+        self.marks.append((False, index))
+        return self
+
+    def mark_key(self, str key):
+        self.marks.append((True, key))
+        return self
+
+    @property
+    def has_value(self):
+        """Check has value set"""
+        return self._value is not _NOT_SET
+
+    def set_value(self, value):
+        """Set value if not set"""
+        if self._value is _NOT_SET:
+            self._value = value
+
+    @property
+    def value(self):
+        """The invalid value"""
+        if self._value is _NOT_SET:
+            return None
+        return self._value
+
+    @property
+    def field(self):
+        """First level index or key, usually it's the field"""
+        if not self.marks:
+            return None
+        __, index_or_key = self.marks[-1]
+        return index_or_key
+
+    @property
+    def position(self):
+        """A string which represent the position of invalid.
+
+        For example:
+
+            {
+                "tags": ["ok", "invalid"],  # tags[1]
+                "user": {
+                    "name": "invalid",      # user.name
+                    "age": 500              # user.age
+                }
+            }
+        """
+        cdef str text = ''
+        cdef bint is_key
+        for is_key, index_or_key in reversed(self.marks):
+            if is_key:
+                text = '%s.%s' % (text, index_or_key)
+            else:
+                if index_or_key == -1:
+                    text = '%s[]' % text
+                else:
+                    text = '%s[%d]' % (text, index_or_key)
+        if text and text[0] == '.':
+            text = text[1:]
+        return text
+
+    @property
+    def message(self):
+        """Error message"""
+        if self.args:
+            return self.args[0]
+        else:
+            return None
+
+    def __str__(self):
+        return _format_error(self.args, self.position)
+
+
+class Invalid(ValidrError):
+    """Data invalid"""
+    def __str__(self):
+        cdef str value_clause = None
+        if self.has_value:
+            value_clause = 'value=%s' % _format_value(self.value)
+        return _format_error(self.args, self.position, value_clause)
+
+
+class ModelInvalid(Invalid):
+    """Model data invalid"""
+    def __init__(self, errors):
+        if not errors:
+            raise ValueError('errors is required')
+        self.errors = errors
+        message = errors[0].message or 'invalid'
+        message += ' ...total {} errors'.format(len(errors))
+        super().__init__(message)
+
+    def __str__(self):
+        error_line_s = []
+        for ex in self.errors:
+            error_line_s.append('{} is {}'.format(ex.position, ex.message))
+        return '; '.join(error_line_s)
+
+
+class SchemaError(ValidrError):
+    """Schema error"""
+    def __str__(self):
+        cdef str value_clause = None
+        if self.has_value:
+            value_clause = 'schema=%s' % self.value.repr(prefix=False, desc=False)
+        return _format_error(self.args, self.position, value_clause)
+
+
+cdef class mark_index:
+    """Add current index to Invalid/SchemaError"""
+
+    cdef int index
+
+    def __init__(self, index=-1):
+        """index = -1 means the position is uncertainty"""
+        self.index = index
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is not None and issubclass(exc_type, ValidrError):
+            exc_val.mark_index(self.index)
+
+
+cdef class mark_key:
+    """Add current key to Invalid/SchemaError"""
+
+    cdef str key
+
+    def __init__(self, key):
+        self.key = key
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is not None and issubclass(exc_type, ValidrError):
+            exc_val.mark_key(self.key)
+
+
+class py_mark_index(mark_index): pass
+class py_mark_key(mark_key): pass
+
+
 cdef bint is_dict(obj):
     # use isinstance(obj, Mapping) is slow,
     # hasattr check can speed up about 30%
diff --git a/src/validr/exception.py b/src/validr/exception.py
deleted file mode 100644
index f6309db..0000000
--- a/src/validr/exception.py
+++ /dev/null
@@ -1,4 +0,0 @@
-try:
-    from ._exception_c import *  # noqa: F401,F403
-except ImportError:
-    from ._exception_py import *  # noqa: F401,F403
diff --git a/src/validr/model.py b/src/validr/model.py
index 913b757..55e2a38 100644
--- a/src/validr/model.py
+++ b/src/validr/model.py
@@ -1,11 +1,13 @@
 """
-Model class is a convenient way to use schema, it's inspired by data class but works differently.
+Model class is a convenient way to use schema, it's inspired by data class
+but works differently.
 """
-from .exception import Invalid, ModelInvalid, mark_key
 from .schema import Compiler, Schema, T
+from .validator import Invalid, ModelInvalid
 from .validator import py_get_dict_value as get_dict_value
 from .validator import py_get_object_value as get_object_value
 from .validator import py_is_dict as is_dict
+from .validator import py_mark_key as mark_key
 
 
 class ImmutableInstanceError(AttributeError):
diff --git a/src/validr/model.pyi b/src/validr/model.pyi
index 4a5a6c9..6b2e32e 100644
--- a/src/validr/model.pyi
+++ b/src/validr/model.pyi
@@ -1,7 +1,12 @@
 import typing
+
 from .schema import Compiler
 
 
+class ImmutableInstanceError(AttributeError):
+    ...
+
+
 M = typing.TypeVar('M')
 
 
diff --git a/src/validr/schema.py b/src/validr/schema.py
index 0722b34..7a44144 100644
--- a/src/validr/schema.py
+++ b/src/validr/schema.py
@@ -28,19 +28,29 @@
     T(schema) -> T
     T.__schema__ -> Schema
 """
-import json
 import copy
 import enum
 import inspect
+import json
 
 from pyparsing import (
-    Group, Keyword, Optional, StringEnd, StringStart, Suppress,
-    ZeroOrMore, quotedString, removeQuotes, replaceWith,
-    pyparsing_common, ParseBaseException,
+    Group,
+    Keyword,
+    Optional,
+    ParseBaseException,
+    StringEnd,
+    StringStart,
+    Suppress,
+    ZeroOrMore,
+    pyparsing_common,
+    quotedString,
+    removeQuotes,
+    replaceWith,
 )
 
-from .validator import builtin_validators
-from .exception import SchemaError, mark_index, mark_key
+from .validator import SchemaError, builtin_validators
+from .validator import py_mark_index as mark_index
+from .validator import py_mark_key as mark_key
 
 
 def _make_keyword(kwd_str, kwd_value):
diff --git a/src/validr/schema.pyi b/src/validr/schema.pyi
index 926abd6..b5d2d22 100644
--- a/src/validr/schema.pyi
+++ b/src/validr/schema.pyi
@@ -1,10 +1,26 @@
-import typing
+from typing import Callable, Iterable, Union
+
+
+class Schema:
+    def repr(self, *, prefix=True, desc=True) -> str:
+        ...
+
+    def copy(self) -> "Schema":
+        ...
 
 
 class Builder:
-    def __getitem__(self, keys: typing.Iterable[str]) -> "Builder": ...
+    def __getitem__(self, keys: Iterable[str]) -> "Builder": ...
     def __getattr__(self, name: str) -> "Builder": ...
     def __call__(self, *args, **kwargs) -> "Builder": ...
 
 
 T: Builder
+
+
+class Compiler:
+    def __init__(self, validators: dict = None):
+        ...
+
+    def compile(self, schema: Union[Schema, Builder]) -> Callable:
+        ...
diff --git a/src/validr/validator.pyi b/src/validr/validator.pyi
new file mode 100644
index 0000000..01f7026
--- /dev/null
+++ b/src/validr/validator.pyi
@@ -0,0 +1,74 @@
+from typing import Callable, Dict, List
+
+
+class ValidrError(ValueError):
+
+    @property
+    def value(self): ...
+
+    @property
+    def field(self) -> str: ...
+
+    @property
+    def position(self) -> str: ...
+
+    @property
+    def message(self) -> str: ...
+
+
+class Invalid(ValidrError):
+    ...
+
+
+class ModelInvalid(Invalid):
+    ...
+
+
+class SchemaError(ValidrError):
+    ...
+
+
+def validator(string: bool = None, *, accept=None, output=None):
+    ...
+
+
+builtin_validators: Dict[str, Callable]
+
+
+def create_enum_validator(
+    name: str,
+    items: List,
+    string: bool = True,
+) -> Callable:
+    ...
+
+
+def create_re_validator(
+    name: str,
+    r: str,
+    maxlen: int = None,
+    strip: bool = False,
+) -> Callable:
+    ...
+
+
+class py_mark_index():
+    def __init__(self, index: int = -1):
+        ...
+
+    def __enter__(self):
+        ...
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        ...
+
+
+class py_mark_key():
+    def __init__(self, key: str):
+        ...
+
+    def __enter__(self):
+        ...
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        ...
diff --git a/tests/smoke.py b/tests/smoke.py
index c69a65a..8540246 100644
--- a/tests/smoke.py
+++ b/tests/smoke.py
@@ -1,5 +1,7 @@
 import os
-from validr import T, modelclass, asdict
+from platform import python_implementation
+
+from validr import T, asdict, modelclass
 
 
 @modelclass
@@ -29,13 +31,15 @@ def check_pure_python():
 
 
 def check_c_python():
-    import validr._validator_py  # noqa: F401
     import validr._validator_c  # noqa: F401
+    import validr._validator_py  # noqa: F401
 
 
 def check():
     check_feature()
-    if os.getenv('VALIDR_SETUP_MODE') == 'py':
+    is_cpython = python_implementation() == 'CPython'
+    is_mode_py = os.getenv('VALIDR_SETUP_MODE') == 'py'
+    if is_mode_py or not is_cpython:
         check_pure_python()
     else:
         check_c_python()