Python | Count number of items in a dictionary value that is a list

In Python, dictionary is a collection which is unordered, changeable and indexed. Dictionaries are written with curly brackets, and they have keys and values. It is used to hash a particular key.

A dictionary has multiple key:value pairs. There can be multiple pairs where value corresponding to a key is a list. To check that the value is a list or not we use the isinstance() method which is inbuilt in Python.

isinstance() method takes two parameters:

object - object to be checked
classinfo - class, type, or tuple of classes and types

It return a boolean whether the object is an instance of the given class or not.

Let’s discuss different methods to count number of items in a dictionary value that is a list.

Method #1 Using in operator

# Python program to count number of items 
# in a dictionary value that is a list. 
def main(): 
  
    # defining the dictionary 
    d = {'A' : [1, 2, 3, 4, 5, 6, 7, 8, 9], 
        'B' : 34, 
        'C' : 12, 
        'D' : [7, 8, 9, 6, 4] } 
  
    # using the in operator 
    count = 0
    for x in d: 
        if isinstance(d[x], list): 
            count += len(d[x]) 
    print(count) 
  
# Calling Main     
if __name__ == '__main__': 
    main() 

Output:

Method #2: Using list comprehension

# Python program to count number of items 
# in a dictionary value that is a list. 
def main(): 
  
    # defining the dictionary 
    d = {'A' : [1, 2, 3, 4, 5, 6, 7, 8, 9], 
        'B' : 34, 
        'C' : 12, 
        'D' : [7, 8, 9, 6, 4] } 
  
    # using list comprehension 
    print(sum([len(d[x]) for x in d if isinstance(d[x], list)])) 
      
if __name__ == '__main__': 
    main() 

Output:

Method #3: Using dict.items()

# Python program to count number of items 
# in a dictionary value that is a list. 
def main(): 
  
    # defining the dictionary 
    d = { 'A' : [1, 2, 3, 4, 5, 6, 7, 8, 9], 
        'B' : 34, 
        'C' : 12, 
        'D' : [7, 8, 9, 6, 4] } 
  
    # using dict.items() 
    count = 0
    for key, value in d.items(): 
        if isinstance(value, list): 
              count += len(value) 
    print(count) 
      
if __name__ == '__main__': 
    main() 

Output:

Method #4: Using enumerate()

# Python program to count number of items 
# in a dictionary value that is a list. 
def main(): 
  
    # defining the dictionary 
    d = {'A' : [1, 2, 3, 4, 5, 6, 7, 8, 9], 
        'B' : 34, 
        'C' : 12, 
        'D' : [7, 8, 9, 6, 4] } 
  
    # using enumerate() 
    count = 0
    for x in enumerate(d.items()): 
  
        # enumerate function returns a tuple in the form 
        # (index, (key, value)) it is a nested tuple 
        # for accessing the value we do indexing x[1][1] 
        if isinstance(x[1][1], list): 
            count += len(x[1][1]) 
    print(count) 
  
if __name__ == '__main__': 
    main() 

Output:

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