Python list function | count()

count() is an inbuilt function in Python that returns count of how many times a given object occurs in list.

Syntax :

list_name.count(object)

Parameters :

Object is the things whose count is to be returned.

Returns :

count() method returns count of how many times obj occurs in list.

Exception :

If more then 1 parameter is passed in count() method, 
it returns a TypeError.

Code #1

# Python3 program to count the number of times 
# an object appears in a list using count() method  
  
list1 = [1, 1, 1, 2, 3, 2, 1]  
  
# Counts the number of times 1 appears in list1 
print(list1.count(1))  
  
list2 = ['a', 'a', 'a', 'b', 'b', 'a', 'c', 'b']  
  
# Counts the number of times 'b' appears in list2 
print(list2.count('b'))  
  
list3 = ['Cat', 'Bat', 'Sat', 'Cat', 'cat', 'Mat'] 
  
# Counts the number of times 'Cat' appears in list3 
print(list3.count('Cat')) 

Output :

4
3
2

Code #2 : TypeError

# Python3 program to demonstrate 
# the error in count() method 
  
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)

Code #3

# Python3 program to count the number of times 
# an object appears in a list using count() method  
  
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 list1 
print(list1.count(('Cat', 'Bat'))) 
  
# Count the number of times sublist 
# '[1, 2]' appears in list1 
print(list1.count([1, 2])) 

Output :

2
2

Practical Application :

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

# 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 list 
print ([ [l, lst.count(l)] for l in set(lst)]) 
  
# To get the number of occurrences  
# of each item in a dictionary 
print (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}

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