![]() ![]() And " Python 3.9+" means it's compatible with Python 3.9 or above (including 3.10, etc). In all the docs there are examples compatible with each version of Python (when there's a difference).įor example " Python 3.6+" means it's compatible with Python 3.6 or above (including 3.7, 3.8, 3.9, 3.10, etc). If you can choose a more recent version of Python for your project, you will be able to take advantage of that extra simplicity. The syntax using typing is compatible with all versions, from Python 3.6 to the latest ones, including Python 3.9, Python 3.10, etc.Īs Python advances, newer versions come with improved support for these type annotations and in many cases you won't even need to import and use the typing module to declare the type annotations. It exists specifically to support these type hints. To declare those types and the internal types, you can use the standard Python module typing. And it's possible to declare them, even with their internal types. These types that have internal types are called " generic" types. And the internal values can have their own type too. There are some data structures that can contain other values, like dict, list, set and tuple. Here’s the classic syntax, which you need to use if support 3.6+.Def get_items ( item_a : str, item_b : int, item_c : float, item_d : bool, item_e : bytes ): return item_a, item_b, item_c, item_d, item_d, item_e Generic types with type parameters ¶ MyPy validates the Python version you ask for Nicer NamedTuple definition (very popular in Python 3 code) Static typing has some great features worth checking out: Try to turn on as much as possible, and increase it until you can run with full strict checking. Personally, I recommend using pre-commit to run all your checks except pytest (and that only because it’s likely slow), and including MyPy in your pre-commit testing. Third party libraries that are typed sometimes forget this last step, by the way! MyPy also looks in typeshed, which is a library full of type hints for (mostly) the standard library. You can add configuration to pyproject.toml (and a little bit to the files themselves), or you can go all the way and pass -strict, which will turn on everything.įor a library to support typing, it has to a) add types using any of the three methods, and b) add a py.typed empty file to indicate that it’s okay to look for types inside it. By default:Īll untyped variables and return values will be AnyĬode inside untyped functions is not checked at all Configuration #īy default, MyPy does as little as possible, so that you can add it iteratively to a code base. If you are writing code for a Raspberry Pi, for example, you could add the stubs for the Pi libraries, and then validate your code, without ever even installing the Pi-only libraries! 10.1.3. MyPy will pull the types from your stubs. If you have a library you don’t control, you can add “type stubs” for it, then give MyPy your stubs directory. You can annotate compiled files or libraries you don’t control this way. This is important for type stubs or for cases where you don’t want to add imports or touch the original code. They can be in a separate file with the same name but with a. Required mostly for Python 2 code, and still requires the proper imports (one reason why the packaging section is so important, depending on libraries like backports is important). But MyPy can find it and tell you there’s a logic issue, your function cannot take None like it claims it can. ![]() You may not run into None often, until you are in a critical situation. Your test suite may have forgotten to run with a None input. Tmp.py:5: note: Left operand is of type "Optional" Found 1 error in 1 file (checked 1 source file) Tmp.py:5: error: Unsupported operand types for * ( "None" and "int") ![]()
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