Index of Non-Zero Elements in Python list Last Updated : 05 Feb, 2025 Comments Improve Suggest changes Like Article Like Report We are given a list we need to find all indexes of Non-Zero elements. For example, a = [0, 3, 0, 5, 8, 0, 2] we need to return all indexes of non-zero elements so that output should be [1, 3, 4, 6].Using List ComprehensionList comprehension can be used to find the indices of non-zero elements by iterating through the list with enumerate(). It collects indices where element is not zero into a new list. Python a = [0, 3, 0, 5, 8, 0, 2] # Use list comprehension with enumerate() to get indices of non-zero elements ind = [i for i, val in enumerate(a) if val != 0] print(ind) Output[1, 3, 4, 6] Explanation:enumerate(a) provides both index and value, and list comprehension filters indices where the value is non-zero.Result is a list of indices of non-zero elements.Using a LoopWe can use a loop with enumerate() to iterate through the list and check for non-zero values. If a value is non-zero we append its index to a separate list. Python a = [0, 3, 0, 5, 8, 0, 2] ind = [] for i in range(len(a)): # If the element is non-zero, append its index to the list if a[i] != 0: ind.append(i) print(ind) Output[1, 3, 4, 6] Using NumPyNumPy provides numpy.nonzero() function which returns indices of non-zero elements in an array. Converting a list to a NumPy array allows efficient retrieval of these indices. Python import numpy as np a = [0, 3, 0, 5, 8, 0, 2] # Use np.nonzero() to get indices of non-zero elements and convert to a list ind = np.nonzero(a)[0].tolist() print(ind) Output[1, 3, 4, 6] Explanation:np.nonzero(a) returns a tuple containing an array of indices where elements in a are non-zero, and [0] extracts the first element (the indices array)..tolist() converts the NumPy array of indices into a regular Python list. Comment More infoAdvertise with us Next Article Index of Non-Zero Elements in Python list manjeet_04 Follow Improve Article Tags : Python Python list-programs Practice Tags : python Similar Reads Get Index of Multiple List Elements in Python In Python, retrieving the indices of specific elements in a list is a common task that programmers often encounter. There are several methods to achieve this, each with its own advantages and use cases. 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