da-dada added the comment:
my use case is different (I do a loop), but what I expected from the docs (just
for fun!)
class Ddefault:
def __init__(self):
vars(self).setdefault('default', self.set_default() if not 'default' in
vars(self) else self.default)
vars(self).setde
Rémi Lapeyre added the comment:
The documentation is correct, in Python argument are computed before the
call to a function, not when they are used. You can try other functions
than dict.setdefault() and see that the behaviour is always the same.
Le dim. 8 déc. 2019 à 22:47, da-dada a écrit :
da-dada added the comment:
I have no problem of making my programme run properly (asking first if in dict
etc), but I just read the docu of dict.setdefault
setdefault(key[, default])
If key is in the dictionary, return its value. If not, insert key with a value
of default and return default
Eric V. Smith added the comment:
Right. If you want the value only calculated once, then just call it once.
You might be interested in collections.defaultdict, which takes a factory
function, and only calls it as needed.
--
nosy: +eric.smith
resolution: -> not a bug
stage: -> resol
Rémi Lapeyre added the comment:
>
>
> def __init__(self):
> vars(self).setdefault('default', self.set_default())
> vars(self).setdefault('default', self.set_default())
>
This code is equivalent to
def __init__(self):
x = self.set_default()
vars(self).set
New submission from da-dada :
from the docu I expected at the second call just a return of value and not a
second calculation: there is room for improvement, as Elon Musk would say..
class Ddefault:
def __init__(self):
vars(self).setdefault('default', self.set_default())
v
