Given a list of booleans, write a Python program to find the count of true booleans in the given list.
Examples:
Input : [True, False, True, True, False] Output : 3 Input : [False, True, False, True] Output : 2
Method #1: Using List comprehension One simple method to count True booleans in a list is using list comprehension.
Python3
# Python3 program to count True booleans in a listdef count(lst): return sum(bool(x) for x in lst)# Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Method #2 : Using sum()
Python3
# Python3 program to count True booleans in a listdef count(lst): return sum(lst) # Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
A more robust and transparent method to use sum is given below.
Python3
def count(lst): return sum(1 for x in lst if x) |
Method #3 : count() method
Python3
# Python3 program to count True booleans in a listdef count(lst): return lst.count(True) # Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Method #4 : filter()
Python3
# Python3 program to count True booleans in a listdef count(lst): return len(list(filter(None, lst))) # Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Method #5 : Using for loop
Python3
# Python3 program to count True booleans in a listdef count(lst): c=0 for i in lst: if(i==True): c+=1 return c# Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Method #6 : Using lambda function,len() methods
Python3
# Python3 program to count True booleans in a listdef count(lst): return len(list(filter(lambda x: x == True, lst)))# Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Time Complexity: O(n)
Auxiliary Space: O(n)
Method 7: using operator.countOf() method
Python3
# Python3 program to count True booleans in a listimport operator as opdef count(lst): return op.countOf(lst, True)# Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Time Complexity: O(N)
Auxiliary Space : O(1)
Method #8:Using itertools.filterfalse() method
Python3
# Python3 program to count True booleans in a listimport itertoolsdef count(lst): return len(list(itertools.filterfalse(lambda x: x == False, lst)))# Driver codelst = [True, False, True, True, False]print(count(lst)) |
3
Time Complexity: O(N)
Auxiliary Space : O(1)
Method #9: Using numpy:
Algorithm:
- Convert the given list to a NumPy array using np.array() function.
- Count the number of non-zero elements in the array using np.count_nonzero() function.
- Return the count of non-zero elements as the output.
Python3
import numpy as npdef count(lst): arr = np.array(lst) return np.count_nonzero(arr)lst = [True, False, True, True, False]print(count(lst))#This code is contributed by Rayudu |
Output: 3
Time complexity:
Converting the list to a NumPy array takes O(n) time, where n is the length of the list.
Counting the number of non-zero elements in the array takes O(n) time as well.
Therefore, the overall time complexity of the count function is O(n), where n is the length of the input list.
Auxiliary Space:
Converting the list to a NumPy array requires O(n) space as the NumPy array needs to store the same number of elements as the input list.
Counting the number of non-zero elements requires O(1) space as it only needs to store a single integer.
Therefore, the overall space complexity of the count function is O(n), where n is the length of the input list.
