On 10 Ago, 13:58, Jonas Nilsson <j...@spray.se> wrote:
....
You stumbled in two python common pitfalls at once :-)
One, the default arguments issue, was already pointed to you.
The other one is that python variables are just names for objects.
Assigning a variable never mean making a copy, it just means using
another name for the same object.
There used to be a very nice (also graphic) explanationor this
somewhere on the web, but my googling skills failed me this time,
so instead I'll show you the concept using your own code:
class Family:
... def __init__(self, fName, members = []):
... self.fname = fName
... self.members = members
...
mlist = ["Bill"]
f1 = Family("Smiths", mlist )
mlist.append( "John" ) # attempt to not-so-clever reyse of the
sme variable
f2 = Family("Smithers", mlist )
f1.members
['Bill', 'John']
Now my example is a bit contrieved but I'm sure you got the idea : in
your example is better to copy the list with
self.members = members[:].
Better yet, you could make use of python arguments grouping feature :
class Family:
... def __init__(self, fName, *members ):
... self.members = list(members) # because members is a
tuple
... self.fname = fName
...
f1 = Family("Smith")
f1.members.append("Bill")
f2 = Family("Smithers")
f2.members.append("Joe")
f2.members
['Joe']
f1.members
['Bill']
This solves your "no initial member" special case and allows for an
easier syntax for creating class instances
(no brackets involved)
f3 = Family("Bochicchio", "Angelo", "Francesco", "Mario")
f3.members
['Angelo', 'Francesco', 'Mario']
Ciao
----
FB
Thanks everyone.
I was a bit steamed about the problem as it was very unexpected.
Because I couldn't figure out what key words to google on, I resorted
to posting the problem here.
/Jonas
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