Skip to content


Properties accessed twice for classes defined interactively #102

ipython opened this Issue · 2 comments

2 participants


Original Launchpad bug 297501:
Reported by: fdo.perez (Fernando Perez).

Reported on the ipython-user list:

I am experiencing some unusual behavior only when I am directly
working in the ipython shell. The problem involves the get method for
a property.

class MyClass():
   def __init__(self):
       self._x = 3
   def getx(self):
       print "getting x"
       return self._x
   def setx(x):
       print "setting x"
       self._x = x
   x = property(getx, setx)

a = MyClass()
a.x           # prints "getting x" twice
print a.x  # prints "getting x" once

If you stick all this in a file and do 'run', the problem does
not occur. Also, notice that it does not occur in the "print a.x"


[ LP comment 1 by: Fernando Perez, on 2008-11-13 06:47:47.661256+00:00 ]

This is indeed happening, and it's another manifestation of the problems with getattr that have also been reported here:

Similarly, the problem can be avoided by turning %autocall completely off. We still need to investigate whether we can fine-tune %autocall to still work while producing less spurious getattr calls.

@fperez fperez was assigned
IPython: interactive computing in Python member

Honestly, I don't think this is fixable while having autocall active. Autocall needs to inspect the objects fairly aggressively and I don't think we can make it work without triggering getattrs. The answer is simply: if your objects have so many side effects that you can't call getattr on them more than once, disable autocall altogether.

Closing here.

@fperez fperez closed this
@damianavila damianavila referenced this issue
Commit has since been removed from the repository and is no longer available.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Something went wrong with that request. Please try again.