On 20 Nov 2005 20:34:39 -0800, Alex [EMAIL PROTECTED] wrote:
I apologize for asking maybe a very trivial question.
I have a new class object A with slots. One of the slots is, for
example, object spam. Object spam, in turn, also has slots and one of
them is attribute eggs. I need to assign a new value to eggs. In other
words, I need to perform the following:
A.spam.eggs=newValue
The problem is that I have only a string s='spam.eggs' with which to
work, so I cannot write an expression written above. I tried to use
setattr:
setattr(A, s, newValue)
but this does not work. It says that object A does not have attribute
spam.eggs
How would you do it? TIA.
A.spam.eggs=newValue
(which would work) really means, if you break it into steps
(A.spam).eggs = newValue
which is
setattr(getattr(A, 'spam'), 'eggs', newValue)
so you just need to break 'spam.eggs' apart and plug in the pieces.
assuming exactly one dot and no spaces to worry about,
s_spam, s_eggs = s.split('.')
then
setattr(getattr(A, s_spam), s_eggs, newValue)
ought to do the job.
If you have more than one dot, e.g., s = 'spam.eggs.ham'
and eggs has a slot ham that you want to assign to, then you need to
loop on getattr for all but the last name, which you use for the setattr.
Something like (untested)
def setbydots(A, s, val):
names = s.split('.')
for name in names[:-1]:
A = getattr(A, name)
setattr(A, names[-1], val)
This should work for no dots or any number, so long as the reference chain is
valid.
E.g.,
setbydots(A, 'spam.eggs', newValue)
should accomplish
A.spam.eggs=newValue
as you wanted. I hope ;-)
( posting delayed 12 hrs due to news server prob ;-/ )
Regards,
Bengt Richter
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