Basic Usage#
Installing packages with micropip#
micropip can install following types of packages:
Pure Python packages
Pure Python packages are packages that do not have any compiled code.
Most pure Python packages can be installed directly from PyPI with micropip.install
if they have a pure Python wheel. Check if this is the case by trying micropip.install("package-name").
Python packages that contain C-extensions
If a package has C-extensions (or any other compiled codes like Rust), it will not have a pure Python wheel on PyPI.
Trying to install such a package with micropip.install will result in an error like:
ValueError: Can't find a pure Python 3 wheel for 'tensorflow'.
See: https://pyodide.org/en/stable/usage/faq.html#micropip-can-t-find-a-pure-python-wheel
You can use `await micropip.install(..., keep_going=True)` to get a list of all packages with missing wheels.
To install such a package, you need to first build a Python wheels for WASM/Emscripten for it.
Note that pyodide provides several commonly used packages with pre-built wheels.
Those packages can be installed with micropip.install("package-name").
Note
You can find a list of packages with pre-built wheels in the Pyodide documentation. If your package is not in the list, you can build a wheel for it yourself. See the Building packages section of the Pyodide documentation for more information.
Examples#
import micropip
# snoballstemmer is a pure Python package
# and has a pure Python wheel on PyPI
# so it can be installed directly
await micropip.install("snowballstemmer")
# numpy is a package that has C-extensions
# and does not have a pure Python wheel on PyPI
# but it is provided by Pyodide
await micropip.install("numpy")
# It is also possible to install from
# - arbitrary URLs
await micropip.install("https://.../package.whl")
# - local files inside the Pyodide virtual file system
await micropip.install("emfs://.../package.whl")
Advanced usage#
You can pass multiple packages to micropip.install:
await micropip.install(["pkg1", "pkg2"])
A dependency can be refined as per the PEP-508 spec:
await micropip.install("snowballstemmer==2.2.0")
await micropip.install("snowballstemmer>=2.2.0")
await micropip.install("snowballstemmer @ https://.../snowballstemmer.*.whl")
await micropip.install("snowballstemmer[all]")
Disabling dependency resolution#
micropip does dependency resolution by default, but you can disable it, this is useful if you want to install a package that has a dependency which is not a pure Python package, but it is not mandatory for your use case:
await micropip.install("pkg", deps=False)
Constraining indirect dependencies#
Dependency resolution can be further customized with optional constraints:
these modify both direct and indirect dependency resolutions, while direct URLs
in either a requirement or constraint will bypass any other specifiers.
As described in the pip documentation, each constraint:
must provide a name
must provide exactly one of
a set of version specifiers
a URL
must not request any
[extras]
Multiple constraints of the same canonical name are merged.
Invalid constraints will be silently discarded, or logged if verbose is provided.
await micropip.install(
"pkg",
constraints=[
"other-pkg==0.1.1",
"some-other-pkg<2",
"some-other-pkg<3", # merged with the above
"yet-another-pkg@https://example.com/yet_another_pkg-0.1.2-py3-none-any.whl",
# silently discarded # why?
"yet-another-pkg >=1", # previously defined by URL
"yet_another_pkg-0.1.2-py3-none-any.whl", # missing name
"something-completely[different] ==0.1.1", # extras
"package-with-no-version", # missing version or URL
"other-pkg ==0.0.1 ; python_version < '3'", # not applicable
]
)
Over-constrained requirements will fail to resolve, leaving the environment unmodified.
await micropip.install("pkg ==1", constraints=["pkg ==2"])
# ValueError: Can't find a pure Python 3 wheel for 'pkg==1,==2'.
Setting default constraints#
micropip.set_constraints replaces any default constraints for all subsequent
calls to micropip.install that don’t specify constraints:
micropip.set_constraints(["other-pkg ==0.1.1"])
await micropip.install("pkg") # uses defaults, if needed
await micropip.install("another-pkg", constraints=[]) # ignores defaults