The output I\'m getting for my little example app is the following:
Welcome to the Calculator!
Please choose what you\'d like to do:
0: Addition
1: Subtracti
Perhaps the following, then your calculator can use arbitrary number base (e.g. hex, binary, base 7! etc): (untested)
def convert(str):
try:
base = 10 # default
if ':' in str:
sstr = str.split(':')
base, str = int(sstr[0]), sstr[1]
val = int(str, base)
except ValueError:
val = None
return val
val = convert(raw_input("Enter value:"))
# 10 : Decimal
# 16:a : Hex, 10
# 2:1010 : Binary, 10