sklearn.base.clone - incorrect/unclear error about 'get_params' when called on class

Describe the bug

When I clone a class, rather than instance of that class, I get error message saying that ‘get_params is not implemented’, even though it is

Steps/Code to Reproduce

from sklearn.base  import clone
from sklearn.linear_model import LogisticRegression
clone(LogisticRegression)

Expected Results

# TypeError Cannot clone object '<class 'sklearn.linear_model.logistic.LogisticRegression'>' (type <class 'type'>): it is a class rather than an instance of a class.

Actual Results

# TypeError: Cannot clone object '<class 'sklearn.linear_model.logistic.LogisticRegression'>' (type <class 'type'>): it does not seem to be a scikit-learn estimator as it does not implement a 'get_params' methods.
LogisticRegression.get_params
# <function sklearn.base.BaseEstimator.get_params(self, deep=True)>

This should be quite straightforward to fix, we could just change the comparison here to two different comparisons with different warnings. The current warning is unclear, and makes debugging harder.

Versions

System: python: 3.7.4 (default, Aug 13 2019, 15:17:50) [Clang 4.0.1 (tags/RELEASE_401/final)] executable: /opt/anaconda3/bin/python machine: Darwin-18.7.0-x86_64-i386-64bit

Python deps: pip: 19.2.3 setuptools: 41.4.0 sklearn: 0.21.3 numpy: 1.17.2 scipy: 1.3.1 Cython: 0.29.13 pandas: 0.25.1

[olicairns]

@glemaitre Thanks, yes I’ll do that soon just working out how to clone repo, run tests ect.

[glemaitre]

@olicairns do you want to propose a PR?