4. Firmware API Reference

This chapter describes modules (function and class libraries) which are built into MicroPython. There are a few categories of modules:

  • Modules which implement a subset of standard Python functionality and are not intended to be extended by the user.
  • Modules which implement a subset of Python functionality, with a provision for extension by the user (via Python code).
  • Modules which implement MicroPython extensions to the Python standard libraries.
  • Modules specific to a particular port and thus not portable.

Note about the availability of modules and their contents: This documentation in general aspires to describe all modules and functions/classes which are implemented in MicroPython. However, MicroPython is highly configurable, and each port to a particular board/embedded system makes available only a subset of MicroPython libraries. For officially supported ports, there is an effort to either filter out non-applicable items, or mark individual descriptions with “Availability:” clauses describing which ports provide a given feature. With that in mind, please still be warned that some functions/classes in a module (or even the entire module) described in this documentation may be unavailable in a particular build of MicroPython on a particular board. The best place to find general information of the availability/non-availability of a particular feature is the “General Information” section which contains information pertaining to a specific port.

Beyond the built-in libraries described in this documentation, many more modules from the Python standard library, as well as further MicroPython extensions to it, can be found in the micropython-lib repository.

4.2 Micropython libraries

The following list contains the standard Python libraries, MicroPython-specific libraries and Pycom specific modules that are available on our boards.

The standard Python libraries have been “micro-ified” to fit in with the philosophy of MicroPython. They provide the core functionality of that module and are intended to be a drop-in replacement for the standard Python library.


Some modules are available by an u-name, and also by their non-u-name. The non-u-name can be overridden by a file of that name in your package path. For example, import json will first search for a file json.py or directory json and load that package if it is found. If nothing is found, it will fallback to loading the built-in ujson module.