narwhals-dev
Make `import_optional_dependency` util
We should make such a util, which can take an optional argument specifying the minimum version. Then we can raise unified and consistent error messages
Sounds interesting @MarcoGorelli - could you explain a bit more on this?
hey @mikeweltevrede ! good to hear from you again!
we have some places where we import optional dependencies inline, e.g.
https://github.com/narwhals-dev/narwhals/blob/5f1f19f542e13dd3efc217f56291b16db88b88d6/narwhals/dataframe.py#L503-L507
We should probably have a helper function which does this, and a custom narwhals error for missing optional dependencies
pandas has something similar (import_optional_dependency in their source code) which we could probably use (with attribution, of course)
pandas has something similar (
import_optional_dependencyin their source code) which we could probably use (with attribution, of course)
Here's the polars one - which is pretty clean and well-documented
https://github.com/pola-rs/polars/blob/0ca485a88a217eab2d55efbd981dfd68709e63be/py-polars/polars/dependencies.py#L225-L287
AFAIK, if we want the imported modules to be understood by a type checker - we'll need 1 function per-import.
Example
_module_not_found
from __future__ import annotations
from importlib import import_module
from importlib.util import find_spec
from types import ModuleType
from typing import Any
from typing import Literal
def _module_not_found(module_name: str, **kwds: Any) -> ModuleNotFoundError:
some_logic_transforming_kwds = repr(kwds)
msg = f"{module_name!r} not found.\n{some_logic_transforming_kwds!r}"
return ModuleNotFoundError(msg)
importlib-only
By default, we know nothing about the the contents of the module.
def import_optional_1(module_name: Literal["polars", "pandas"], **kwds: Any):
if find_spec(module_name):
return import_module(module_name)
raise _module_not_found(module_name=module_name, **kwds)
Single function
Better than the first option.
But we can't capture @overload(s)
def import_optional_2(module_name: Literal["polars", "pandas"], **kwds: Any):
if module_name == "polars" and find_spec("polars"):
import polars as pl
return pl
elif module_name == "pandas" and find_spec("pandas"):
import pandas as pd
return pd
raise _module_not_found(module_name=module_name, **kwds)
Multiple functions
So far, this is the only route I've found that would preserve typing
def import_polars(**kwds: Any):
if find_spec("polars"):
import polars as pl
return pl
raise _module_not_found(module_name="polars", **kwds)
def import_pandas(**kwds: Any):
if find_spec("pandas"):
import pandas as pd
return pd
raise _module_not_found(module_name="pandas", **kwds)
[!IMPORTANT] The warning above is something we don't want to lose
