TypeError: GridSearchCV scoring has wrong type

TypeError: invalid scoring type

$ python -c "from sklearn.model_selection import GridSearchCV; from sklearn.linear_model import LogisticRegression; GridSearchCV(LogisticRegression(), param_grid={'C':[1]}, scoring=123).fit([[0],[1]], [0,1])"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: scoring must be a string, callable, or dict of such

Why this happens

scoring expects a valid metric string, a callable with signature (estimator, X, y), or a dict mapping names to scorers.

Fix

Use a supported metric name like 'accuracy' or a proper callable.

Wrong code

from sklearn.model_selection import GridSearchCV
from sklearn.linear_model import LogisticRegression
GridSearchCV(LogisticRegression(), {'C':[1]}, scoring=123)

Fixed code

from sklearn.model_selection import GridSearchCV
from sklearn.linear_model import LogisticRegression
GridSearchCV(LogisticRegression(), {'C':[1]}, scoring='accuracy')