[python, condition, index, ndarray] Get indices of value in a np array (因為符合條件的可能有很多位置, 所以傳回的是一個 ndarray)

arrData = np.array([1, 2, 3, 4, 5, 6, 8]) 

arrIndex = np.where(arrData == 3)[0] # Get the index where data == 3

print("arrIndex  = ", arrIndex )

Result

[2]

Reference

1. https://numpy.org/doc/stable/reference/generated/numpy.where.html