def list_classes():
print()
classes = db.get_classes()
class_header()
for cl in classes:
print_class(cl)
print()
def choose_class():
print()
classes = []
class_header()
for i, cl in enumerate(db.get_classes()):
print(str(i).rjust(2), end='\t')
print_class(cl)
classes.append(cl[0])
class_number = input('Please select class by entering its number:')
class_number = int(class_number)
if class_number < 0 or class_number > len(classes) - 1:
return None
return classes[class_number]