def square_list(list_to_square):
    '''prints each item of list_to_square squared'''
    for next_number in list_to_square:
        print(next_number ** 2)   
   
students = [('Alice', 2016), ('Bob', 2017), ('Charlie', 2019)]

def print_students(student_list):
    '''print out the name and year of each student tuple in student_list'''
    for student in student_list:
        (name, year) = student
        print("Name: " + name + ", class year " + str(year))

def list_length(some_list):
    '''returns the length of some_list'''
    count = 0
    for element in some_list:
        count += 1
    return count

def extract_upper(string):
    '''return a new string consisting only of the uppercase letters
    in string'''
    uppercase = ''
    for char in string:
        if char.isupper():
            uppercase += char
    return uppercase