Python List count() method

#Python List count() method| 来源: 网络整理| 查看: 265

Python List count() method returns the count of how many times a given object occurs in a List.

Python List count() method Syntax

Syntax: list_name.count(object)

Parameters:

object: is the item whose count is to be returned.

Returns: Returns the count of how many times object occurs in the list.

Exception:

TypeError: Raises TypeError If more than 1 parameter is passed in count() method.Python List count() method ExamplePython3

list2 = ['a', 'a', 'a', 'b', 'b', 'a', 'c', 'b']print(list2.count('b'))

Output:

3Example 1: Count Tuple and List Elements Inside List

Count occurrences of List and Tuples inside a list using count() method.

Python3

list1 = [ ('Cat', 'Bat'), ('Sat', 'Cat'), ('Cat', 'Bat'), ('Cat', 'Bat', 'Sat'), [1, 2], [1, 2, 3], [1, 2] ] # Counts the number of times 'Cat' appears in list1print(list1.count(('Cat', 'Bat'))) # Count the number of times sublist# '[1, 2]' appears in list1print(list1.count([1, 2]))

Output:

2 2Exceptions while using Python list count() methodTypeError

Python list count() method raises TypeError when more than 1 parameter is passed.

Python3

list1 = [1, 1, 1, 2, 3, 2, 1] # Error when two parameters is passed.print(list1.count(1, 2))

Output:

Traceback (most recent call last): File "/home/41d2d7646b4b549b399b0dfe29e38c53.py", line 7, in print(list1.count(1, 2)) TypeError: count() takes exactly one argument (2 given)Practical Application

Let’s say we want to count each element in a list and store it in another list or say dictionary.

Python3

# Python3 program to count the number of times# an object appears in a list using count() method lst = ['Cat', 'Bat', 'Sat', 'Cat', 'Mat', 'Cat', 'Sat'] # To get the number of occurrences# of each item in a listprint ([ [l, lst.count(l)] for l in set(lst)]) # To get the number of occurrences# of each item in a dictionaryprint (dict( (l, lst.count(l) ) for l in set(lst)))

Output:

[['Mat', 1], ['Cat', 3], ['Sat', 2], ['Bat', 1]] {'Bat': 1, 'Cat': 3, 'Sat': 2, 'Mat': 1}My Personal Notes arrow_drop_up

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