IPython/tests/refbug.py

"""Minimal script to reproduce our nasty reference counting bug.

The problem is related to https://bugs.launchpad.net/ipython/+bug/269966

The original fix for that appeared to work, but JD Hunter found a matplotlib
example which, when run twice in a row, would break.  The problem were
references held by open figures to internals of Tkinter.

This code reproduces the problem that John saw, without matplotlib.  We can
thus use it for our test suite.
"""

#-----------------------------------------------------------------------------
# Module imports
#-----------------------------------------------------------------------------
import sys

from IPython import ipapi

#-----------------------------------------------------------------------------
# Globals
#-----------------------------------------------------------------------------
ip = ipapi.get()

if not '_refbug_cache' in ip.user_ns:
    ip.user_ns['_refbug_cache'] = []


aglobal = 'Hello'
def f():
    return aglobal

cache = ip.user_ns['_refbug_cache']
cache.append(f)

def call_f():
    for func in cache:
        print 'lowercased:',func().lower()