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lst = [1,2,3,4,1] I want to know 1 occurs twice in this list, is there any efficient way to do?
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Use the COUNTIF function to count how many times a particular value appears in a range of cells. For more information, see COUNTIF function.
Method 1: Using the index() Method The index() function in Python searches for an element in a list and returns its index. If the element occurs more than once in the list, the index of its first occurence is returned and if the element is not present in the list, the function raises a ValueError.
lst.count(1) would return the number of times it occurs. If you're going to be counting items in a list, O(n) is what you're going to get.
The general function on the list is list.count(x), and will return the number of times x occurs in a list.
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