list as paremeters...

[shagshag13]

hello,

i have an unexpected behaviour that i didn't understand, can someone explain
this to me ?

>>> def doit(s, stack = []):
 if s == '':
  return stack

 stack.append(s[:1])
 return doit(s[1:], stack)

>>> doit('this')
['t', 'h', 'i', 's']
>>> doit('this')
['t', 'h', 'i', 's', 't', 'h', 'i', 's']
>>> doit('this')
['t', 'h', 'i', 's', 't', 'h', 'i', 's', 't', 'h', 'i', 's']

and so on ... i would expect it to stuck to
>>> doit('this')
['t', 'h', 'i', 's']

why does this 'stack' remind of previous call ?

thanks.