This expression is true in Python: {} .keys (). Insert (0, "") == None. What for?

Question

Take a look at my Python session:

>>> {} .keys (). insert (0, "") == None
True

and

>>> k = {} .keys ()
>>> k
[]
>>> k.insert (0, "")
>>> k
['']

Why??

PS . Thanks for the help! Python has a very strange design - it doesn't support chaining:

This is the root of my problem ...

+3

gavenkoa 08 Feb 13 at 20:11

2 answers

You are checking the return type for None

case 1, which will evaluate to True

. Python insert

returnsNone

+2

karthikr 08 Feb 13 at 20:15

ecatmur · Accepted Answer · 2013-02-08T20:13:50+0000

list.insert

returns None

; when k

you print, you print the new state of the list.