pySimpleLeapYearTest

# Simple Python script to accept a year from user input, check it is within a certain range,
# and check if it is a leap year

def isleap(yr):
    # This function receives an integer year in "yr" (which has already been tested for valid range)
    # It returns True if the year is a leap year
    # It returns False if the year is not a leap year
    # The function will produce valid result for all years 1901 to 2099 inclusive
    # For this range of years, all years that are exactly divisible by 4 are leap years
    if yr % 4:
        return False        # The division did NOT result in zero, therefore yr is not leap

    return True             # yr is leap


# Here I have written code that will loop indefinitely
while True:

    # input() always gives us a string
    uyear = input("Enter a year from 1901 to 2099 inclusive: ")

    # Here we test if the string uyear contains digits only
    if uyear.isdigit():

        # Yes, uyear is numeric. We can convert it to an integer
        year = int(uyear)           # now year is an integer

        # Here we test if the year is greater than 1900 and less than 2100
        # (it is important not to allow 1900 or 2100, as those years break the simple divisable by 4 rule)
        if 1900 < year < 2100:
            # Yes the year is valid (within the range we are interested in)
            # Call our function that tests if the year is a leap year or not
            if isleap(year):
                # The function returned "True" therefore the year is a leap year
                print(f"Year {year} is a leap year")
            else:
                # the function returned False, therefore the year is not a leap year
                print(f"Year {year} is not a leap year")

            # Here we say "continue" to go around the While True loop again, without printing "invalid"
            continue

    # Either the user input was not numeric, OR the year was out of range
    print("Invalid year")

    # Now the code will go around the "while True" loop again