> num = [1,2]
> num.append(3)
> num
[1, 2, 3]
> num.append('a')
> num
[1, 2, 3, 'a']
> num.append(6,7)
Traceback (most recent call last):
 File "<pyshell#8>", line 1, in <module>
  num.append(6,7)
TypeError: append() takes exactly one argument (2 given)
> num.append([6])
> num
[1, 2, 3, 'a', [6]]
> num.append({'a'})
> num
[1, 2, 3, 'a', [6], set(['a'])]

> num=[1,2]
> num.extend([5])
> num
[1, 2, 5]
> num.extend(['b'])
> num
[1, 2, 5, 'b']
> num.extend(6,7)
Traceback (most recent call last):
 File "<pyshell#29>", line 1, in <module>
  num.extend(6,7)
TypeError: extend() takes exactly one argument (2 given)