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() |
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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() |
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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() |
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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() |
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