ImportError: cannot import name 'CLoader' from 'yaml'

TL;DR

CLoader only exists when PyYAML compiled against libyaml. Plenty of installs skip it (pure-python wheel, missing compiler, musl/alpine). If you just need speed-safe parsing, use yaml.SafeLoader instead, it is always there. If you truly need the C loader, reinstall so it builds: pip install --no-binary :all: pyyaml with a compiler and libyaml headers present.

The error

ImportError: cannot import name 'CLoader' from 'yaml'

Fix it

1. Try from yaml import SafeLoader / CSafeLoader and confirm which exists: python -c "from yaml import SafeLoader; print('ok')". Expected: prints ok

2. For the C loader, install build deps (gcc, libyaml-dev / libyaml-devel), then pip install --force-reinstall --no-binary :all: pyyaml. Expected: pip build log shows building against libyaml; from yaml import CLoader then works

3. Or sidestep it: most code that wants CLoader runs fine on SafeLoader, just a bit slower. Expected: your YAML still parses, no import error

When this applies

• ImportError: cannot import name 'CLoader' (or CParser / CDumper) from 'yaml'
• plain import yaml works but the C names dont

When it does NOT apply

• ModuleNotFoundError: No module named 'yaml' (package not installed at all)
• you need the C loader for correctness rather than speed (you almost certainly dont)

Tool and version notes

PyYAML 5.x/6.x. Manylinux wheels bundle libyaml so CLoader usually exists there; alpine/musl, --no-binary installs, and some conda builds are the common pure-python cases.

Other ways this shows up

ImportError: cannot import name 'CSafeLoader' from 'yaml'

Same fix. All four C names (CLoader, CParser, CDumper, CSafeLoader) come from the same optional extension.

Why it happens

The C extension is a build-time option, not a separate package. If the wheel you got was pure python, the names simply arent defined, and no pip flag can conjure them without a rebuild.

Edge cases

• On alpine, you need yaml-dev plus gcc and musl-dev before the reinstall.
• Some distros split libyaml headers into a -dev package; the runtime lib alone isnt enough to build against.