MicroPython libraries

This chapter describes modules (function and class libraries) which are built into MicroPython. This documentation in general aspires to describe all modules and functions/classes which are implemented in the MicroPython project. However, MicroPython is highly configurable, and each port to a particular board/embedded system may include only a subset of the available MicroPython libraries.

With that in mind, please 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 system. 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 MicroPython port.

On some ports you are able to discover the available, built-in libraries that can be imported by entering the following at the REPL:

help('modules')

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 micropython-lib.

Python standard libraries and micro-libraries

The following 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.

• array – arrays of numeric data
• asyncio — asynchronous I/O scheduler
• binascii – binary/ASCII conversions
• builtins – builtin functions and exceptions
• cmath – mathematical functions for complex numbers
• collections – collection and container types
• errno – system error codes
• gc – control the garbage collector
• gzip – gzip compression & decompression
• hashlib – hashing algorithms
• heapq – heap queue algorithm
• io – input/output streams
• json – JSON encoding and decoding
• math – mathematical functions
• os – basic “operating system” services
• platform – access to underlying platform’s identifying data
• random – generate random numbers
• re – simple regular expressions
• select – wait for events on a set of streams
• socket – socket module
• ssl – SSL/TLS module
• struct – pack and unpack primitive data types
• sys – system specific functions
• time – time related functions
• zlib – zlib compression & decompression
• _thread – multithreading support

MicroPython-specific libraries

Functionality specific to the MicroPython implementation is available in the following libraries.

• bluetooth — low-level Bluetooth
• btree – simple BTree database
• cryptolib – cryptographic ciphers
• deflate – deflate compression & decompression
• machine — functions related to the hardware
• micropython – access and control MicroPython internals
• network — network configuration
• openamp – provides standard Asymmetric Multiprocessing (AMP) support
• uctypes – access binary data in a structured way
• mutex — mutex module
• uping — Ping another computer
• urequests — Related functions of HTTP client
• vfs – virtual filesystem control

Libraries specific to the OpenMV Cam

The following libraries are specific to the OpenMV Cam.

• pyb — functions related to the board
• stm — functionality specific to STM32 MCUs
• sensor — camera sensor
• image — machine vision
• ml — Machine Learning
• gif — gif recording
• mjpeg — mjpeg recording
• audio — Audio Module
• display — display driver
• fir — thermal sensor driver (fir == far infrared)
• tv — tv shield driver
• cpufreq — CPU Frequency Control
• buzzer — buzzer driver
• imu — imu sensor
• rpc — rpc library
• rtsp — rtsp library
• omv — OpenMV Cam Information
• gt911 — Touch Screen Driver
• ft5x06 — Touch Screen Driver
• tfp410 — DVI/HDMI Controller

Third-party libraries on the OpenMV Cam

The following third-party libraries are built-in to your OpenMV Cam’s firmware:

ulab — numpy-like array manipulation library

pid — Proportional/Integral/Derivative Control

bno055 — IMU Driver

Examples scripts are located in OpenMV IDE under the IMU Shield examples folder.

ssd1306 — OLED Driver

tb6612 — Stepper Motor Driver

Examples scripts are located in OpenMV IDE under the Motor Shield examples folder.

modbus — modbus protocol library

Examples scripts are located in OpenMV IDE under the Modbus examples folder.

mqtt — mqtt protocol library

Examples scripts are located in OpenMV IDE under the WiFi Shield examples folder.

vl53l1x — ToF Distance Sensor Driver

Examples scripts are located in OpenMV IDE under the Distance Shield examples folder.

Extending built-in libraries from Python

A subset of the built-in modules are able to be extended by Python code by providing a module of the same name in the filesystem. This extensibility applies to the following Python standard library modules which are built-in to the firmware: array, binascii, collections, errno, gzip, hashlib, heapq, io, json, os, platform, random, re, select, socket, ssl, struct, time zlib, as well as the MicroPython-specific machine module. All other built-in modules cannot be extended from the filesystem.

This allows the user to provide an extended implementation of a built-in library (perhaps to provide additional CPython compatibility or missing functionality). This is used extensively in micropython-lib, see Package management for more information. The filesystem module will typically do a wildcard import of the built-in module in order to inherit all the globals (classes, functions and variables) from the built-in.

In MicroPython v1.21.0 and higher, to prevent the filesystem module from importing itself, it can force an import of the built-in module it by temporarily clearing sys.path during the import. For example, to extend the time module from Python, a file named time.py on the filesystem would do the following:

_path = sys.path
sys.path = ()
try:
  from time import *
finally:
  sys.path = _path
  del _path

def extra_method():
  pass

The result is that time.py contains all the globals of the built-in time module, but adds extra_method.

In earlier versions of MicroPython, you can force an import of a built-in module by appending a u to the start of its name. For example, import utime instead of import time. For example, time.py on the filesystem could look like:

from utime import *

def extra_method():
  pass

This way is still supported, but the sys.path method described above is now preferred as the u-prefix will be removed from the names of built-in modules in a future version of MicroPython.

Other than when it specifically needs to force the use of the built-in module, code should always use import module rather than import umodule.