Long integers: to L or not to L?

[Dimitris Garanatsios]

Dimitris Garanatsios wrote:
> ...but if you ever call function h() you might get:
> 
> Traceback (most recent call last):
>   File "script1.py", line 14, in ?
>     h()
>   File "script1.py", line 11, in h
>     i = h1()
>   File "script1.py", line 4, in h1
>     i = i + 1
> UnboundLocalError: local variable 'i' referenced before assignment
> 
> This is because nested scopes in python is a new addition which is not 
> supported in my version (2.2.1) unless a "from __future__ import ..." is 
> used. So in this case the "i = 0" statement is not seen inside h1(). 
> Again, you may consult python's documentation for more details about new 
> feature additions...

A correction on my remark: I saw that nested scopes was part of python 
2.2.1 (sorry about my mistake...). So the error gets raised when you try 
to assign a new value to variable i (an immutuable object: integer) in a 
scope that it does not exist (although it can be "seen" in that scope). 
So if you change h1 to

def h1():
     j = i + 1
     print 1, j
     if j == 5:
         return j
     else:
         j = h1()
         return j

You won't get the above UnboundLocalError (assuming nested scopes are 
supported in your version of python) but instead a

RuntimeError: maximum recursion depth exceeded

because j will never reach value 5 :-)
If you want to use nested scopes to change the value of an object that 
is defined in an outter scope, use muttuable objects:

def h():
     i = [0]
     def h1():
         i[0] = i[0] + 1
         print 1, i[0]
         if i[0] == 5:
             return i[0]
         else:
             i[0] = h1()
             return i[0] # this will never get executed
     i[0] = h1()
     print 2, i[0]

This might not be pretty, but it will happily run as expected :-)

Again, sorry for my mistake
Dimitris