Python | Program to count number of lists in a list of lists
Given a list of lists, write a Python program to count the number of lists contained within the list of lists.
Examples:
Input : [[1, 2, 3], [4, 5], [6, 7, 8, 9]] Output : 3 Input : [[1], ['Bob'], ['Delhi'], ['x', 'y']] Output : 4
Method #1 : Using len()
# Python3 program to Count number # of lists in a list of lists def countList(lst): return len(lst) # Driver codelst = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]print(countList(lst)) |
Output:
3
Method #2 : Using type()
Use a for loop and in every iteration to check if the type of the current item is a list or not, and accordingly increment ‘count’ variable. This method has a benefit over approach #1, as it works well for a list of heterogeneous elements.
# Python3 program to Count number # of lists in a list of lists def countList(lst): count = 0 for el in lst: if type(el)== type([]): count+= 1 return count # Driver codelst = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]print(countList(lst)) |
Output:
3
A one-liner alternative approach for the above code is given below:
def countList(lst): return sum(type(el)== type([]) for el in lst) |
Method #3 : Using isinstance() method
# Python3 program to Count number # of lists in a list of lists def countList(lst): return sum(isinstance(i, list) for i in lst) # Driver codelst = [[1, 2, 3], [4, 5], [6, 7, 8, 9]]print(countList(lst)) |
Output:
3
