Package management¶
Installing packages with mip¶
Network-capable boards include the mip module, which can install packages
from micropython-lib and from third-party sites (including GitHub).
mip (“mip installs packages”) is similar in concept to Python’s pip tool,
however it does not use the PyPI index, rather it uses micropython-lib
as its index by default. mip will automatically fetch compiled
.mpy file when downloading from micropython-lib.
The most common way to use mip is from the REPL:
>>> import mip
>>> mip.install("pkgname") # Installs the latest version of "pkgname" (and dependencies)
>>> mip.install("pkgname", version="x.y") # Installs version x.y of "pkgname"
>>> mip.install("pkgname", mpy=False) # Installs the source version (i.e. .py rather than .mpy files)
mip will detect an appropriate location on the filesystem by searching
sys.path for the first entry ending in /lib. You can override the
destination using target, but note that this path must be in sys.path to be
able to subsequently import it.:
>>> mip.install("pkgname", target="third-party")
>>> sys.path.append("third-party")
As well as downloading packages from the micropython-lib index, mip can also
install third-party libraries. The simplest way is to download a file directly:
>>> mip.install("http://example.com/x/y/foo.py")
>>> mip.install("http://example.com/x/y/foo.mpy")
When installing a file directly, the target argument is still supported to set
the destination path, but mpy and version are ignored.
The URL can also start with github: as a simple way of pointing to content
hosted on GitHub:
>>> mip.install("github:org/repo/path/foo.py") # Uses default branch
>>> mip.install("github:org/repo/path/foo.py", version="branch-or-tag") # Optionally specify the branch or tag
More sophisticated packages (i.e. with more than one file, or with dependencies)
can be downloaded by specifying the path to their package.json.
>>> mip.install("http://example.com/x/package.json")
>>> mip.install("github:org/user/path/package.json")
If no json file is specified, then “package.json” is implicitly added:
>>> mip.install("http://example.com/x/")
>>> mip.install("github:org/repo") # Uses default branch of that repo
>>> mip.install("github:org/repo", version="branch-or-tag")
Using mip on the Unix port¶
On the Unix port, mip can be used at the REPL as above, and also by using -m:
$ ./micropython -m mip install pkgname-or-url
$ ./micropython -m mip install pkgname-or-url@version
The --target=path, --no-mpy, and --index arguments can be set:
$ ./micropython -m mip install --target=third-party pkgname
$ ./micropython -m mip install --no-mpy pkgname
$ ./micropython -m mip install --index https://host/pi pkgname
Installing packages with mpremote¶
The mpremote tool also includes the same functionality as mip and
can be used from a host PC to install packages to a locally connected device
(e.g. via USB or UART):
$ mpremote mip install pkgname
$ mpremote mip install pkgname@x.y
$ mpremote mip install http://example.com/x/y/foo.py
$ mpremote mip install github:org/repo
$ mpremote mip install github:org/repo@branch-or-tag
The --target=path, --no-mpy, and --index arguments can be set:
$ mpremote mip install --target=/flash/third-party pkgname
$ mpremote mip install --no-mpy pkgname
$ mpremote mip install --index https://host/pi pkgname
Installing packages manually¶
Packages can also be installed (in either .py or .mpy form) by manually copying
the files to the device. Depending on the board this might be via USB Mass Storage,
the mpremote tool (e.g. mpremote fs cp path/to/package.py :package.py),
webrepl, etc.
Writing & publishing packages¶
Publishing to micropython-lib is the easiest way to make your package
broadly accessible to MicroPython users, and automatically available via
mip and mpremote and compiled to bytecode. See
https://github.com/micropython/micropython-lib for more information.
To write a “self-hosted” package that can be downloaded by mip or
mpremote, you need a static webserver (or GitHub) to host either a
single .py file, or a package.json file alongside your .py files.
A typical package.json for an example mlx90640 library looks like:
{
"urls": [
["mlx90640/__init__.py", "github:org/micropython-mlx90640/mlx90640/__init__.py"],
["mlx90640/utils.py", "github:org/micropython-mlx90640/mlx90640/utils.py"]
],
"deps": [
["collections-defaultdict", "latest"],
["os-path", "latest"],
["github:org/micropython-additions", "main"]
],
"version": "0.2"
}
This includes two files, hosted at a GitHub repo named
org/micropython-mlx90640, which install into the mlx90640 directory on
the device. It depends on collections-defaultdict and os-path which will
be installed automatically from the micropython-lib. The third
dependency installs the content as defined by the package.json file of the
main branch of the GitHub repo org/micropython-additions.
Freezing packages¶
When a Python module or package is imported from the device filesystem, it is compiled into bytecode in RAM, ready to be executed by the VM. For a .mpy file, this conversion has been done already, but the bytecode still ends up in RAM.
For low-memory devices, or for large applications, it can be advantageous to instead run the bytecode from ROM (i.e. flash memory). This can be done by “freezing” the bytecode into the MicroPython firmware, which is then flashed to the device. The runtime performance is the same (although importing is faster), but it can free up significant amounts of RAM for your program to use.
The downside of this approach is that it’s much slower to develop, because you have to flash the firmware each time, but it can be still useful to freeze dependencies that don’t change often.
Freezing is done by writing a manifest file and using it in the build, often as part of a custom board definition. See the MicroPython manifest files guide for more information.