Nevar forget

gistfile1.py

# object instances as default arguments are evil
def nevar_forget(constarg={}):
  constarg[len(constarg)] = 'the catch'
  print(constarg)
  return constarg

assert(nevar_forget() == {0: 'the catch'})
assert(nevar_forget() == {0: 'the catch', 1: 'the catch'})
assert(nevar_forget() == {0: 'the catch', 1: 'the catch', 2: 'the catch'})

# class methods are no different
class NevarForget(object):
  
  def __init__(self, thedict={}):
    self.thedict = thedict


first = NevarForget()
first.thedict[1] = 'oh yes'
assert(first.thedict == {1: 'oh yes'})

second = NevarForget()
second.thedict[2] = 'oh no'

assert(first.thedict == {1: 'oh yes', 2: 'oh no'})
assert(second.thedict == {1: 'oh yes', 2: 'oh no'})