annoying behavior

Peter Otten __peter__ at web.de
Tue Sep 28 19:16:31 CEST 2004


Elbert Lev wrote:

> # here is the problem I ran into:
> 
> class foo:
>     def __init__(self, host):
>         self.f()
>         self.r = True
>     
>     def f(self):
>         if self.r:
>             #<do something>
>             pass
>         else:
>             #<do something else>
>             pass
> 
> f = foo("1234")
> 
> #here is the output:
> 
> #Traceback (most recent call last):
> #  File "G:\MyProjects\Python\Little\inconv.py", line 16, in ?
> #    f = foo("1234")
> #  File "G:\MyProjects\Python\Little\inconv.py", line 5, in __init__
> #    self.f()
> #  File "G:\MyProjects\Python\Little\inconv.py", line 9, in f
> #    if self.r:
> #AttributeError: foo instance has no attribute 'r'
> 
> # I understand why does this happen, but, to tell the truth,

...you don't seem to. An attribute is not there until you set it.

> # this feature is very annoying.
> # Are there any plans to relax this restriction?
> # In 3.0 :)?

No chance. Even as a non-developer I dare say that.
Either modify __init__():

def __init__(self):
    self.r = False # for example
    self.f()    
    self.r = True

or change f():

def f(self):
    if hasattr(self, "r"):
        # do something
    else:
        # do something else

Peter




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