Numpy<\/a> is a popular Python module that allows you to perform various operations on numbers. It is commonly used for its computational power, by scientists, data analysts and businesses. You can use its where() function to determine the index of a given item in a list. Here is an example to illustrate it.<\/p>\n\n\n\nimport numpy as np
a = [1, 2, 3, 4, 5, 3]
item = 3
np_array = np.array(a)
indexes = np.where(np_array==item)
print(indexes)<\/pre>\n\n\n\nHere is the output.<\/p>\n\n\n\n
(array([2, 5]),)<\/pre>\n\n\n\nIn the above code, we first import Numpy library. Then we create a Numpy array from list a. Then we pass this array in where() function with the condition checking if item=3 exists in it. We store all result indexes in a result array.<\/p>\n\n\n\n
This is a very useful solution for large lists because Numpy arrays are more efficient than Python lists.<\/p>\n\n\n\n