Grid Search

from sklearn.datasets import load_iris
from sklearn.model_selection import GridSearchCV
from sklearn.neighbors import KNeighborsClassifier

X, y = load_iris(return_X_y=True)
gs = GridSearchCV(KNeighborsClassifier(), {'n_neighbors': [1, 3, 5]}, cv=5).fit(X, y)
print(gs.best_params_)

{'n_neighbors': 5}