Python | Count true booleans in a list
Last Updated :
30 Mar, 2023
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 list
def count(lst):
return sum(bool(x) for x in lst)
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Method #2 : Using sum()
Python3
# Python3 program to count True booleans in a list
def count(lst):
return sum(lst)
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
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 list
def count(lst):
return lst.count(True)
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Method #4 : filter()
Python3
# Python3 program to count True booleans in a list
def count(lst):
return len(list(filter(None, lst)))
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Method #5 : Using for loop
Python3
# Python3 program to count True booleans in a list
def count(lst):
c=0
for i in lst:
if(i==True):
c+=1
return c
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Method #6 : Using lambda function,len() methods
Python3
# Python3 program to count True booleans in a list
def count(lst):
return len(list(filter(lambda x: x == True, lst)))
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Time Complexity: O(n)
Auxiliary Space: O(n)
Method 7: using operator.countOf() method
Python3
# Python3 program to count True booleans in a list
import operator as op
def count(lst):
return op.countOf(lst, True)
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
Time Complexity: O(N)
Auxiliary Space : O(1)
Method #8:Using itertools.filterfalse() method
Python3
# Python3 program to count True booleans in a list
import itertools
def count(lst):
return len(list(itertools.filterfalse(lambda x: x == False, lst)))
# Driver code
lst = [True, False, True, True, False]
print(count(lst))
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 np
def 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.
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