Question

Reading the Python 3.2 tutorial here, towards the end one of the examples is

a[:] = []

Is this equivalent to

a = []

? If it is, why did they write a[:] instead of a? If it isn’t, what is the difference?

Answer 1

They are not equivalent. These two examples should get you to understand the difference.

Example 1:

>>> b = [1,2,3]
>>> a = b
>>> a[:] = []
>>> print b
[]

Example 2:

>>> b = [1,2,3]
>>> a = b
>>> a = []
>>> print b
[1,2,3]