Python all Function with Examples

The all() built-in function in Python returns True if all elements in an iterable are true. If the iterable contains at least one false element, the function returns False. In this blog post, let us explore the syntax, arguments, and return value of the all() function. Additionally, we’ll provide three unique examples of how the all() function can be used, and discuss when it is most appropriate to use this function.

Table of Contents

Introduction to Python all() functions
Syntax and Arguments
Examples

1. Checking if all elements in a list are positive
2. Checking if all elements in a list are non-empty
3. Checking if all keys in a dictionary are non-empty
4. Checking if all elements in a list are even
5. Checking if all elements in a list of strings start with the same character

When to use Python all() function
Conclusion

Syntax and Arguments:

The syntax of the all() function is as follows:

all(iterable)

Here, iterable is the argument we pass to the function, and it can be any iterable object, such as a list, tuple, set, or dictionary.

Return Value: The all() function returns True if all elements in the iterable are true, and False if at least one element is false.

Examples:

Example 1: Checking if all elements in a list are positive

nums = [2, 4, 6, 8, 10]
if all(num > 0 for num in nums):
    print("All given elements are positive.")
else:
    print("Not all given elements are positive.")

Output: All given elements are positive.

Example 2: Checking if all elements in a list are non-empty

fruits = ["apple", "banana", "", "orange"]
if all(fruit for fruit in fruits):
    print("All elements are non-empty.")
else:
    print("Not all elements are non-empty.")

Output: Not all elements are non-empty.

Example 3: Checking if all keys in a dictionary are non-empty

person = {"name": "John", "age": 25, "address": ""}
if all(person[key] for key in person):
    print("All keys are non-empty.")
else:
    print("Not all keys are non-empty.")

Output: Not all keys are non-empty.

Example 4: Checking if all elements in a list are even

nums = [2, 4, 6, 8, 9]
if all(num % 2 == 0 for num in nums):
    print("All elements are even.")
else:
    print("Not all elements are even.")

Output: Not all elements are even.
In this example, we use the all() function to check if all elements in the ‘nums’ list are even. Since 9 is an odd number, the function returns False.

Example 5: Checking if all elements in a list of strings start with the same character

fruits = ["apple", "apricot", "avocado", "artichoke"]
if all(fruit[0] == "a" for fruit in fruits):
    print("All elements start with 'a'.")
else:
    print("Not all elements start with 'a'.")

Output: All elements start with ‘a’.

When to use Python all() function:

The all() function can be used in scenarios where we need to check if all elements in an iterable meet a certain condition. Some common use cases include:

Validating user inputs: For example, checking if all fields in a form have been filled out before submitting the form.
Checking if all elements in a list meet a certain condition: For example, checking if all values in a list are positive.
Checking if all keys in a dictionary meet a certain condition: For example, checking if all keys in a dictionary are non-empty.

Conclusion:

In this blog post, we explored the all() function in Python, which is used to check if all elements in an iterable are true. We discussed the syntax, arguments, and return value of the function, and provided examples of how it can be used in different scenarios. The all() function is a useful tool to have in your Python toolkit, particularly when working with iterable objects.