namespace issue?

[Michael Powe]

Hello,

This looks like a namespace issue described in <learning python> but
it doesn't make sense to me and I don't know how to fix it.

ex 1:

>>> def GetNum():
...	AC = raw_input("Area Code: ")
...	PN = raw_input("Phone Number: ")
...	if not AC : AC = '503'
...	if not PN : PN = '000-0000'
...	Ph = AC + PN[:3] + '-' + PN[3:]
...	return Ph
... 
>>> ok = GetNum()
Area Code: 503
Phone Number: 2243187
>>> ok
'503224-3187'

ex 2:

>>> def GetNum2():	
... 	AC = raw_input("Area Code: ")
... 	PN = raw_input("Phone Number: ")
...	if not PN : PN = '000-0000'
...	if not AC : AC = '503'
...	if len(PN) < 8 and not string.find(PN,'-'):
...		Ph = PN[:3] + '-' + PN[3:]
...	return Ph
... 
>>> ok = GetNum2()
Area Code: 434
Phone Number: 2243187
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 8, in GetNum2
UnboundLocalError: local variable 'Ph' referenced before assignment

The issue is, I don't understand why the problem appears with variable
'Ph' in the second instance but not in the first.  It seems obvious
that it comes about because of the conditional.

Also, on a side note, what is the default data type for input gathered
from raw_input()?  Is it a string?

Thanks for any help.

mp