Python: Check if a given function returns True for every element in a list

Last update on April 19 2025 12:57:52 (UTC/GMT +8 hours)

Check All True for Function

Write a Python program to check if a given function returns True for every element in a list.

Use all() in combination with map() and fn to check if fn returns True for all elements in the list.

Sample Solution:

Python Code:

# Define a function 'every' that takes a list 'lst' and an optional function 'fn' as input.
# The default function 'fn' is set to an identity function.
def every(lst, fn=lambda x: x):
    # Use the 'all' function to check if every element in the list 'lst' satisfies the condition specified by 'fn'.
    return all(map(fn, lst))
	
# Call the 'every' function with different lists and conditions, and print the results.
print(every([4, 2, 3], lambda x: x > 1))
print(every([4, 2, 3], lambda x: x < 1))
print(every([4, 2, 3], lambda x: x == 1))

Sample Output:

True
False
False

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to check if a provided function returns True for every element in a list and list the indices where it fails.
Write a Python program to verify that all elements in a list satisfy a condition defined by a lambda function and then output a boolean result.
Write a Python program to test if a given predicate holds for all elements in a list and return a custom error message if not.
Write a Python program to check if all elements of a list are even using a provided function, and output the result along with the count of elements checked.

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