Python List count() method

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

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 Example

Since the first occurrence of character b is on the 3rd index, the output is 3. Here we are using Python count to get our count.

Python3

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

Output:

3

Count Tuple and List Elements Inside List

Count occurrences of List and Python Tuples inside a list using the Python 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 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

Exceptions while using Python list count() method

TypeError

List count() in Python 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 Python list and store it in another list or say Python 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 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}