cramjam

 1import os
 2
 3# Backend is picked once, at import. `pip install cramjam[pure-rust]` then set
 4# CRAMJAM_BACKEND=pure-rust to use libcramjam's pure-Rust codecs instead of C.
 5backend = os.environ.get("CRAMJAM_BACKEND", "c")
 6if backend == "pure-rust":
 7    try:
 8        from cramjam_pure_rust.cramjam import *
 9    except ImportError as e:
10        raise ImportError(
11            "CRAMJAM_BACKEND=pure-rust but cramjam-pure-rust isn't installed; `pip install cramjam[pure-rust]`"
12        ) from e
13elif backend == "c":
14    from .cramjam import *
15else:
16    raise ValueError(f"CRAMJAM_BACKEND must be 'c' or 'pure-rust', got {backend!r}")