The documentation of dis.findlabels says:

> dis.findlabels(code)
> Detect all offsets in the code object code which are jump targets, and return a list of these offsets.

But the implementation actually expects a raw compiled bytecode.

>>> def f():pass

>>> dis.findlabels(f.__code__)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/laike9m/.pyenv/versions/3.7.4/lib/python3.7/dis.py", line 424, in findlabels
    for offset, op, arg in _unpack_opargs(code):
  File "/Users/laike9m/.pyenv/versions/3.7.4/lib/python3.7/dis.py", line 408, in _unpack_opargs
    for i in range(0, len(code), 2):
TypeError: object of type 'code' has no len()

>>> dis.findlabels(f.__code__.co_code)
[]

Since the other functions in the dis module all accept a code object rather than compiled code, I would suggest change the code instead of documentation.

Plus, this function does not seem to be tested anywhere. I can make a PR if this issue is confirmed.

dis.findlabels() always worked with a byte code. And the docstring correctly describes this.

I think this is a documentation issue. The documentation fix should be backported to all maintained Python versions.

If you want to make dis.findlabels() accepting a code object, it would be a new feature and it may be only added in future Python release (3.9). It needs a separate issue. In any case the documentation bug should be fixed in maintained versions.

I've created a PR to fix documentation.
https://github.com/python/cpython/pull/19274

I'll create a new issue for making the function accept a code object.

New changeset b74468e233a5137ff518e61eff65ca2d8833e38a by laike9m in branch 'master':
bpo-40122: Updated documentation for dis.findlabels() (GH-19274)
https://github.com/python/cpython/commit/b74468e233a5137ff518e61eff65ca2d8833e38a

New changeset 00c779fd9c0a9e7586681a44e35607c1113b5014 by Miss Islington (bot) in branch '3.7':
bpo-40122: Updated documentation for dis.findlabels() (GH-19274)
https://github.com/python/cpython/commit/00c779fd9c0a9e7586681a44e35607c1113b5014

New changeset 77c623ba3d084e99d68c30f368bd7fbd7f175b60 by Miss Islington (bot) in branch '3.8':
bpo-40122: Updated documentation for dis.findlabels() (GH-19274)
https://github.com/python/cpython/commit/77c623ba3d084e99d68c30f368bd7fbd7f175b60