MicroPython libraries

Warning

Important summary of this section

• MicroPython provides built-in modules that mirror the functionality of the Python standard library (e.g. os, time), as well as MicroPython-specific modules (e.g. bluetooth, machine).

• Most Python standard library modules implement a subset of the functionality of the equivalent Python module, and in a few cases provide some MicroPython-specific extensions (e.g. array, os)

• Due to resource constraints or other limitations, some ports or firmware versions may not include all the functionality documented here.

• To allow for extensibility, some built-in modules can be extended from Python code loaded onto the device filesystem.

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.