Check the principles of minimalist code in the intro to the first challenge.

In the Code tab you will find code that is missing a single character in order to pass the tests. However, your goal is to submit a function that is as minimalist as possible. Use the tips in the tips section below.

Write a function that returns True if the given positive integer is a prime number and False if it's not.

Tips

Everything you write after if, not, while or around and, or, is, in is interpreted as a boolean.

A function that prints a countdown from the absolute value of x and also prints "hey" if the number is a multiple of 3 and contains the digit "3", could be written as:

def countdown(x):
    if x < 0:
        x = x * -1
    while x > 0:
        if x % 3 == 0:
            if "3" in str(x):
                print(x)
                print("hey")
        else:
            print(x)
        x = x - 1

This can be simplified to:

def countdown(x):
    x = abs(x)
    while x:
        print(x)
        if not x % 3 and "3" in str(x):
            print("hey")
        x -= 1

• abs() gets the absolute value of a number.
• while will interpret x as a boolean, exiting the loop after reaching zero.
• print(x) needs to be called whether x is a "hey number" or not. This can be done outside of any if statement, instead of in both.
• Both conditions x % 3 == 0 and "3" in str(x) need to be True, so they can be joined with an and.

Bonus

A more Pythonistic approach:

def countdown(x):
    for i in range(abs(x), -1, -1):
        print(x)
        if not x % 3 and "3" in str(x):
            print("hey")

Notes

• This is an open series: there isn't a definite list of features for the challenges. Please, do not hesitate to leave your suggestions in the Comment tab.
• Readability is indeed a subjective concept. Let's discuss it! Feel free to leave your opinion in the Comments tab.
• You can find all the exercises in this series over here.