Python: Find the value of the first element in the given list that satisfies the provided testing function

Last update on April 19 2025 12:57:54 (UTC/GMT +8 hours)

First Value Satisfying Function

Write a Python program to find the value of the first element in the given list that satisfies the provided testing function.

Use a list comprehension and next() to return the first element in lst for which fn returns True.

Sample Solution:

Python Code:

# Define a function 'find' that takes a list 'lst' and a function 'fn' as input.
def find(lst, fn):
    # Use a generator expression to find the first element 'x' in the list 'lst' for which 'fn(x)' is true.
    # The 'next' function is used to retrieve the first matching element.
    return next(x for x in lst if fn(x))

# Call the 'find' function with a list and a lambda function to find the first odd number in the list.
# Print the result.
print(find([1, 2, 3, 4], lambda n: n % 2 == 1))
# Call the 'find' function again with a lambda function to find the first even number in the list.
# Print the result.
print(find([1, 2, 3, 4], lambda n: n % 2 == 0))

Sample Output:

1
2

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to find the first value in a list that satisfies a custom condition and return it, or None if no value qualifies.
Write a Python program to retrieve the first value in a list that passes a provided test function and print its index.
Write a Python program to find the first palindromic string in a list using a given testing function.
Write a Python program to return the first value in a list that exceeds a specified threshold after applying a lambda function.

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