python - Why list reverse returns Null?

I have example list like this:

l = [1,2,3]


print(l.reverse())
#give None instead [3, 2, 1]

How is that? How can I reverse list?

Answer

How can I reverse list?

The list is being reversed. But list.reverse reverses in place, and does not return anything to the caller. You can verify this by printing the list after calling reverse on it:

>>> l = [1,2,3]
>>> l.reverse()
>>> print(l)
>>> [3, 2, 1]

If in doubt, use the help:

>>> help(list.reverse)

Help on method_descriptor:
reverse(...)
    L.reverse() -- reverse *IN PLACE*

(Python 2.7 documentation)