MicroPython typing.mpy

Why you may need typing.[m]py or typing_extensions.[m]py.

When making use of static typing in Python or MicroPython, you often end up using types that are defined in the CPython typing module. As Python static typing is ‘optimised out’ when the source is compiled to byte-code and then to machinecode, there is virtually no runtime overhead.

However there is one remaining issue, and this is with the import typing or from typing import ...
If you try to run an fully typed MicroPython module or script on a MCU, you will get an error like this:

>>> import example
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "example.py", line 2, in <module>
ImportError: no module named 'typing'

A solution is to add a minimalistic typing.py file to the project, and when your module or script is executed on the MCU, that will be used in place of the CPython typing module.

Install the typing modules to your MCU

To have the least amount of runtime overhead on your MCU, you can (should) used the cross compiled version of the modules to your MCU.

mpremote mip install github:josverl/micropython-stubs/mip/typing.mpy
# and where needed also:
mpremote mip install github:josverl/micropython-stubs/mip/typing_extensions.mpy

Note: The .mpy modules are cross compiled for micropython

Install github:josverl/micropython-stubs/mip/typing.mpy
Downloading github:josverl/micropython-stubs/mip/typing.mpy to /lib
Installing: /lib/typing.mpy

Note that by default mip will install the modules in the /lib folder of the MCU.

Add to your project source

To avoid needing to mip install the modules on every MCU, you can add the modules to your project source. mpremote mip does not have a method to retrieve and store modules localy to your project, but it is simple to copy them from your MCU to your local project.

Assuming you have a project folder src and a lib folder in it, you can copy the modules from the MCU to your project with the following commands:

mpremote cp :lib/typing.mpy src/lib/typing.mpy
mpremote cp :lib/typing_extensions.mpy src/lib/typing_extensions.mpy

Best portability

For best portability across MicroPython ports you can use the typing.py and typing_extensions.py modules. These modules are identical to the typing.mpy and typing_extensions.mpy modules, but are in source form.

Use the same commands as above, but replace the .mpy with .py in the commands.

example code

"""Example typed Micropython module."""
from typing import TYPE_CHECKING, Tuple

def foo(a: int, b: int) -> Tuple[int, str]:
    return a, str(b)

print("Hello, typed world!")
print(f"{foo(1, 2)=}")

About the modules


A minimalistic typing.py module for MicroPython.

Ref: https://github.com/micropython/micropython-lib/pull/584
Author: Andrew Leech

Note: When that PR is merged, or MicroPython itself can provide this functionality, I’ll update the above links to point to micropython-lib.


This module is provided to allow the use of older versions of Python (3.7+).

In CPython the typing_extensions module provide backported type hints from newer versions and enable use of new type system features on older Python versions. For example, typing.TypeGuard is new in Python 3.10, but typing_extensions allows users on previous Python versions to use it too.

As MicroPython has no native typing implementation, the typing_extensions.py module is identical to the typing.py module.