This is just one of many possible solutions:
year = int(input("Enter the year and I will tell you if it's a leap year or not: "))
if year % 4 != 0:
print(str(year) + ' is not a leap year!')
else:
if year % 100 != 0:
print(str(year) + ' is a leap year!')
else:
if year % 400 != 0:
print(str(year) + ' is not a leap year!')
else:
print(str(year) + ' is a leap year!')