davocarli/hintcast

A python package that allows for automatic type-casting based on provided type hints

hintcast

Decorators that allow for automatic type-casting of arguments for a function or strict enforcement of type hints.

Installation Instructions

hintcast is uploaded to PyPI and can be installed using pip install hintcast

Usage Summary

Import whatever decorators you want with an import statement like from hintcast import cast_hints, strict_hints.

Casting Types

• To add automated type-casting to your function/method, use the @cast_hints decorator for your method. If a type cannot be cast, a warning will be logged.
• To attempt to cast but raise a TypeError exception if unable to, pass the keyword argument "strict". E.g. @cast_hints(strict=True).
• To pass None values without casting, pass the keyword argument "cast_none". E.g. @cast_hints(cast_none=False).

Enforcing strict types

• You can also use the @strict_hints decorator. This will NOT attempt to cast the types, but will raise a ValueError if a type not matching your hint is passed.

Usage Examples

Casting Types

from hintcast import cast_hints

@cast_hints
def add_two(num: int, text: str):
    print(repr(num+2))
    print(repr(text+"2"))

Output

>>> add_two("3", 3)
5
'32'
>>> add_two("3", None)
5
'None2'

Casting types without casting NoneType

from hintcast import cast_hints

@cast_hints(cast_none=False)
def add_two(num: int, text: str):
  print(repr(num+2))
  print(repr(text+"2"))

Output

>>> add_two("3", 3)
5
'32'
>>> add_two("3", None)
5
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

Casting types and raising TypeError when type could not be cast

from hintcast import cast_hints

@cast_hints(strict=True)
def add_two(num: int, text: str):
  print(repr(num+2))
  print(repr(tex+"2"))

Output

>>> add_two("3", 3)
5
'32'
>>> add_two("test", 3)
TypeError: Could not convert num to <class 'int'>. invalid literal for int() with base 10: 'test'

Enforcing strict typing without casting

from hintcast import strict_hints

@strict_hints
def add_two(num: int, text: str):
  print(repr(num+2))
  print(repr(text+"2"))

Output

>>> add_two("3", 3)
TypeError: num is not of type <class 'int'>
>>> add_two(3, 3)
TypeError: text is not of type <class 'str'>

Future Development Plans

• Test support for all primitive types
• Add support for checking function return type hints
• Add support for built-in non-primitive data structures such as arrays, lists, etc.
• Add support for hinting of types within lists, dictionaries, etc.
• Add ability to enforce typing project-wide

When all of the functionality above has been implemented and tested, the version number will be incremented to 1.0.0 and this project will leave beta status.