def _num_samples(x):
    if hasattr(x, 'fit'):
        # Don't get num_samples from an ensembles length!
        raise TypeError('Expected sequence or array-like, got '
                        'estimator %s' % x)
    if not hasattr(x, '__len__') and not hasattr(x, 'shape'):
        if hasattr(x, '__array__'):
            x = np.asarray(x)
        else:
            raise TypeError("Expected sequence or array-like, got %s" %
                            type(x))
    if hasattr(x, 'shape'):
        if len(x.shape) == 0:
            raise TypeError("Singleton array %r cannot be considered"
                            " a valid collection." % x)
        return x.shape[0]
    else:
        return len(x)
Return number of samples in array-like x.
dataset/ETHPy150Open scikit-learn/scikit-learn/sklearn/utils/validation.py/_num_samples