# uf.optional

Import optional dependencies without masking broken installs.

A bare `except ImportError` around `import pandas` also swallows the
`ImportError` of a pandas that *is* installed but fails to import (a missing
dependency of pandas, an incompatible binary). The feature then silently turns itself
off. `import_optional` tolerates only the absence of the named package itself.

### Functions

| [`import_optional`](#uf.optional.import_optional)(module_name, \*[, absent])   | Return the imported module, or `None` if the optional package is not installed.   |
|-----------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------|

### uf.optional.import_optional(module_name, , absent=None)

Return the imported module, or `None` if the optional package is not installed.

Only a `ModuleNotFoundError` naming the package itself (the first segment of
`module_name`, or one of `absent`) counts as “not installed”. Every other
failure – a missing submodule, a missing dependency *of* the package, a broken
import inside it – is a broken environment and propagates. A *namespace* package
(a bare directory of that name on `sys.path`, with no `__init__.py`) is not the
package either, so it counts as not installed – which also means a package that is
*legitimately* a namespace package (`google`) can’t be imported with this.

* **Return type:**
  [`Optional`](https://docs.python.org/3/library/typing.html#typing.Optional)[[`ModuleType`](https://docs.python.org/3/library/types.html#types.ModuleType)]

```pycon
>>> import_optional('json').__name__
'json'
>>> import_optional('_uf_no_such_package_') is None
True
>>> import_optional('json.no_such_submodule')
Traceback (most recent call last):
  ...
ModuleNotFoundError: No module named 'json.no_such_submodule'
```