Python 2: why does this function follow with a boolean without if/else conditions?

Here is the sample code I was given to complete:

def is_leap(year):
leap = False

year = int(raw_input())
print is_leap(year)

I've managed to solve it through all sample test cases but I don't understand why leap is assigned False when there are no conditions. What is the point of doing that if I have to redefine leap to True or False again based on the conditions?

Conditions: A year is considered a leap year when:

The year can be evenly divided by 4, is a leap year, unless:

The year can be evenly divided by 100, it is NOT a leap year, unless:

The year is also evenly divisible by 400. Then it is a leap year.

My code:

def is_leap(year):
    leap = False

    if (year % 4 == 0):
       leap = True
    if year % 100 == 0:
        if year % 400 == 0:
            leap = True
        else:
            leap = False
return leap

year = int(raw_input()) print is_leap(year)