Python WTFs

wtf1

>>> a = (1, [2, 3])
>>> a[1] += [4, 5]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> print a
(1, [2, 3, 4, 5])
>>> 

wtf2

>>> a = []
>>> b = a += [1]
  File "<stdin>", line 1
    b = a += [1]
           ^
SyntaxError: invalid syntax
>>> b = a.__iadd__([1])
>>> print b
[1]