setdefault behaviour question

[MRAB]

On 19/05/2012 20:44, pete McEvoy wrote:
> I am confused by some of the dictionary setdefault behaviour, I think
> I am probably missing the obvious here.
>
> def someOtherFunct():
>      print "in someOtherFunct"
>      return 42
>
> def someFunct():
>      myDict = {1: 2}
>      if myDict.has_key(1):
>          print "myDict has key 1"
>      x = myDict.setdefault(1, someOtherFunct())   #<<<<<  I didn't
> expect someOtherFunct to get called here
>      print "x", x
>      y = myDict.setdefault(5, someOtherFunct())
>      print "y", y
>
>
> +++++++++++++++++++++
>
> if I call someFunct() I get the following output
>
> myDict has key 1
> in someOtherFunct
> x 2
> in someOtherFunct
> y 42
>
>
> For the second use of setdefault I do expect a call as the dictionary
> does not the key. Will the function, someOtherFunct, in setdefault
> always be called anyway and it is just that the dictionary will not be
> updated in any way?

The answer is yes.

someOtherFunct() is called and then 1 and the result of
someOtherFunct() are passed as arguments to myDict.setdefault(...).