ValueError: MLP hidden_layer_sizes invalid

ValueError: invalid hidden_layer_sizes

$ python -c "from sklearn.neural_network import MLPClassifier; MLPClassifier(hidden_layer_sizes=0).fit([[0],[1]], [0,1])"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: hidden_layer_sizes must be a tuple of positive integers

Why this happens

Non-tuple or non-positive integers are invalid.

Fix

Use, for example, (100,) or (64,32).

Wrong code

from sklearn.neural_network import MLPClassifier
MLPClassifier(hidden_layer_sizes=0)

Fixed code

from sklearn.neural_network import MLPClassifier
MLPClassifier(hidden_layer_sizes=(100,))