Version checks and optional modules

Branch on behaviour rather than on version numbers where you can. The other functions in this guide do that for you. These three are for the remaining cases. They behave the same on every DOLFINx version.

at_least

fenicsx_compat.at_least(version: str) -> bool

Whether the installed DOLFINx is at least version, compared as packaging versions.

before

fenicsx_compat.before(version: str) -> bool

Whether the installed DOLFINx is strictly older than version. Always the opposite of at_least.

if fenicsx_compat.before("0.11.0.dev0"):
    ...  # 0.10, where facet dofs still have to be permuted by hand

Development builds sort before their release: 0.11.0.dev0 < 0.11.0. To include the nightly builds that led up to a release, compare against X.Y.0.dev0, not X.Y.0.

Use a version check only when the behaviour changed but the API did not, so there is nothing to detect. For example, basix.ufl.real_element() exists on 0.10, but a function space cannot be built from it until 0.11; see real_functionspace.

require_module

fenicsx_compat.require_module(name: str, *, extra: str | None = None) -> types.ModuleType

Imports and returns the module name. If it is missing, raises an ImportError that says what to install: pip install <extra>, or pip install <name> without extra.

gmsh = fenicsx_compat.require_module("gmsh")
h5py = fenicsx_compat.require_module("h5py", extra="scifem[h5py]")