Python Code Example: check leap year in if else statement

A normal year has 365 days. Every four years, however, there is a leap year with 366 days. This is because the earth does not need exactly 365 days to travel once around the sun, but about a quarter day more. So a year has one day more every 4 years.

So that the calculation is correct, there is no leap year every 100 years. Nevertheless, every four hundred years a leap year takes place. This concerns the years 2000, 2400 etc.

Code Example

def isLeapYear(year):
    if (year % 4 != 0):
        return False
    elif (year % 400 == 0):
        return True
    elif (year % 100 == 0):
        return False
    else:
        return True


year = 2020

if(isLeapYear(year)):
    print(str(year) + " is a leap year")
else:
    print(str(year) + " is not a leap year")

Output

2020 is a leap year

Code Explanation

Function Definition: isLeapYear(year)

This function takes a single argument year and returns True if the year is a leap year, and False otherwise. Here’s how it works:

def isLeapYear(year):
    if (year % 4 != 0):
        return False
    elif (year % 400 == 0):
        return True
    elif (year % 100 == 0):
        return False
    else:
        return True

Leap Year Rules

A year is considered a leap year if:

1. It is divisible by 4.
2. However, if it is divisible by 100, it is not a leap year.
3. But if it is divisible by 400, it is a leap year.

The function implements these rules as follows:

Check if the year is not divisible by 4:

if (year % 4 != 0):
    return False

If the year is not divisible by 4, it is not a leap year.

Check if the year is divisible by 400:

elif (year % 400 == 0):
    return True

If the year is divisible by 400, it is a leap year.

Check if the year is divisible by 100:

elif (year % 100 == 0):
    return False

If the year is divisible by 100 (but not by 400), it is not a leap year.

Otherwise, it is a leap year:

else:
    return True

Main Code

After defining the isLeapYear function, the code checks whether a specific year (2020 in this case) is a leap year and prints the result.

year = 2020

if(isLeapYear(year)):
    print(str(year) + " is a leap year")
else:
    print(str(year) + " is not a leap year")

Explanation:

1. Define the year to be checked:python

year = 2020

Here, year is set to 2020.

Call the isLeapYear function and check its result:

if(isLeapYear(year)):
    print(str(year) + " is a leap year")
else:
    print(str(year) + " is not a leap year")

• The isLeapYear(year) function is called with year as its argument.
• If the function returns True, the code prints that the year is a leap year.
• If the function returns False, the code prints that the year is not a leap year.