33. Valid Year

# -----------
# User Instructions
# 
# Modify the valid_year() function to verify 
# whether the string a user enters is a valid 
# year. If the passed in parameter 'year' 
# is not a valid year, return None. 
# If 'year' is a valid year, then return 
# the year as a number. Assume a year 
# is valid if it is a number between 1900 and 
# 2020.
#

def valid_year(year):


#print valid_year('0') 
#=> None    
#print valid_year('-11') 
#=> None
#print valid_year('1950') 
#=> 1950
#print valid_year('2000') 
#=> 2000

# -----------
# User Instructions
# 
# Modify the valid_year() function to verify 
# whether the string a user enters is a valid 
# year. If the passed in parameter 'year' 
# is not a valid year, return None. 
# If 'year' is a valid year, then return 
# the year as a number. Assume a year 
# is valid if it is a number between 1900 and 
# 2020.
#

def valid_year(year):
    if year and year.isdigit():
        year = int(year)
        if year < 2021 and year > 1899:
            return year


#print valid_year('0') 
#=> None    
print valid_year('-11') 
#=> None
print valid_year('1950') 
#=> 1950
print valid_year('2000') 
#=> 2000