fix: provide __version__ attribute (#2573)

* fix: provide __version__ attribute

Pyinstaller is giving an error packaging a script that uses pydantic, "AttributeError: Module 'pydantic' has no attribute '__version__'"

See Issue #2572

* chore: add md file in changes folder

* test: __version__ attribute of pydantic module

changes/2572-paxcodes.md

@@ -0,0 +1 @@
+Add `__version__` attribute to pydantic module.

pydantic/__init__.py

@@ -14,6 +14,8 @@ from .tools import *
 from .types import *
 from .version import VERSION
 
+__version__ = VERSION
+
 # WARNING __all__ from .errors is not included here, it will be removed as an export here in v2
 # please use "from pydantic.errors import ..." instead
 __all__ = [

tests/test_version.py

@@ -0,0 +1,9 @@
+import pydantic
+
+
+def test_version_attribute_is_present():
+    assert hasattr(pydantic, '__version__')
+
+
+def test_version_attribute_is_a_string():
+    assert isinstance(pydantic.__version__, str)