Now what is wrong with this one, This is my second solution and working as expected in my local ide.

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.
def num_teachers(dict_teachers):
    i = 0
    for key in dict_teachers:
        i += 1
    return i

def num_courses(dict_teachers):
    i = 0
    for value in dict_teachers.values():
        i += len(value)
    return i

def courses(dict_teachers):
    course_list = []
    for value in dict_teachers.values():
        course_list += value

    return course_list

def most_courses(dict_teachers):
    max_subs = 0
    max_sub_teacher = ""
    for teacher, course_list in dict_teachers.iteritems():
        if len(course_list) > max_subs:
            max_subs = len(course_list)
            max_sub_teacher = teacher
    return max_sub_teacher