# 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")
    >>> 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"]
      ],
      "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.

## 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.

Language and External Links

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External links
  openmv.io
  forums.openmv.io
  github.com/openmv/openmv
  micropython.org
  forum.micropython.org
  github.com/micropython/micropython