TypeError: load() missing 1 required positional argument: 'Loader'

TL;DR

Since PyYAML 5.1, yaml.load requires a Loader argument (it warns first, then 6.0 made it an error). In almost every case the fix is one word: call yaml.safe_load(stream) instead of yaml.load(stream). Only reach for Loader=yaml.FullLoader if you truly need non-safe constructs.

The error

TypeError: load() missing 1 required positional argument: 'Loader'

Fix it

1. Replace yaml.load(f) with yaml.safe_load(f) and rerun.

Expected: no TypeError; data loads exactly as before for plain dicts/lists/scalars

1. If safe_load rejects something you need (python objects, timestamps quirks), use yaml.load(f, Loader=yaml.FullLoader) instead.

Expected: loads with the full (but still unsafe-construct-free) loader

1. Grep your repo for other bare yaml.load( calls and fix them all at once.

Expected: grep returns no bare yaml.load( calls

When this applies

• TypeError: load() missing 1 required positional argument: 'Loader'
• code written for PyYAML 4.x or older now running on 5.1+

When it does NOT apply

• you actually want the unsafe Loader (rare; think twice, it can execute arbitrary objects)
• CLoader/SafeLoader import errors (different skill)

Tool and version notes

PyYAML 5.1 through 6.x, all supported Pythons. Behavior change landed in 5.1 (warning) and became a hard error in 6.0.

Other ways this shows up

TypeError: load() missing 1 required positional argument: 'Loader' in Ansible or Salt

Same root cause: vendored or pinned old call sites. Fix the call site, dont downgrade PyYAML, since old versions have known deserialization CVEs.

Why it happens

yaml.load without a Loader could construct arbitrary python objects from untrusted input, a real remote-code-execution vector. Upstream made the Loader mandatory so nobody gets the dangerous default by accident.

Edge cases

• safe_load cant load custom python objects on purpose; thats the security boundary, not a bug.
• yaml.unsafe_load exists but you should basically never use it on input you didnt write yourself.