Python - Why doesn't the reverse function doesn't work when given with list but does work with the variable? [duplicate]

Question

Beginner question...

Why does this happen? Why doesn't the reverse function work when given with list but does work with the variable?

>>> a=[1,2].reverse()
>>> a      <--- a is None
>>> a=[1,2]
>>> a.reverse()
>>> a      <--- a is not None and doing what I wanted him to do
[2, 1]
>>>  

Answer 1

1. reverse() doesnt return any value,i.e, it returns None.
2. Reverse() modifies the list in place.

In your first case, you are inturn setting a = None.

In your second case, a is modified by reverse(), and you are able to print the modified "a".

Answer 2

That is because reverse() returns None, but it reverses the order of items in the list.

For example,

>>>a = [1, 2].reverse() # It reversed [1, 2] to [2, 1] but returns None. 
>>>a # The reversed value of [2, 1] disappears, 
# And returned value of None has been assigned to variable a
None

>>>a=[1,2] 
>>>a.reverse() # The order of items of a has been reversed and return None, 
# but there is no variable to take returned value, None.
>>> a
[2, 1]