Expected array-like (array or non-string sequence), got None

Question

I have this code:

X, y = make_classification(n_features=2,n_redundant=0,n_samples=400, random_state=17)
X_train, X_test, y_train, y_test = train_test_split(X,y,test_size=0.3,random_state=17)

clf = DecisionTree(max_depth=4, criterion='gini')
clf.fit(X_train, y_train)

y_pred = clf.predict(X_test)
prob_pred = clf.predict_proba(X_test)
accuracy = accuracy_score(y_test,y_pred)

However, there is an error Expected array-like (array or non-string sequence), got None in the last line accuracy = accuracy_score(y_test,y_pred). How can I fix it?

y_test and/or y_pred are None, debug your program and see where you don't get the expected values. — Guy
– Guy, Commented Jan 5, 2023 at 6:50
@Guy, you are absolutely right, I have 'None' in 'y_pred'. How to solve? — Floda
– Floda, Commented Jan 5, 2023 at 7:00

Corralien · Accepted Answer · 2023-01-05 07:19:25Z

1

Your code with a minor fix works well:

from sklearn.datasets import make_classification
from sklearn.model_selection import train_test_split
from sklearn.tree import DecisionTreeClassifier
from sklearn.metrics import accuracy_score

X, y = make_classification(n_features=2,n_redundant=0,n_samples=400, random_state=17)
X_train, X_test, y_train, y_test = train_test_split(X,y,test_size=0.3,random_state=17)

clf = DecisionTreeClassifier(max_depth=4, criterion='gini')  # Not DecisionTree
clf.fit(X_train, y_train)

y_pred = clf.predict(X_test)
prob_pred = clf.predict_proba(X_test)
accuracy = accuracy_score(y_test,y_pred)

Output:

>>> accuracy
0.8833333333333333

answered Jan 5, 2023 at 7:19

Corralien

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