I Assigned a Variable but it Says I Did Not

Question

Note: I am using Python 3.5 I just started creating a part two to a text based game I made, and here is the code I'm having trouble with:

import random

def game():
    randomIp = random.randint(10, 999)

    def tutorial():
        global randomIp

        print('Hello.')
        print(randomIp + '.' + randomIp + '.' + randomIp + '.' + randomIp)

The problem that kept coming up was:

File "C:\Users\Anony\Desktop\SICCr4k2BrokeFold\SICCr4k2Broke.py", line 18, in tutorial
  print(randomIp + '.' + randomIp + '.' + randomIp + '.' + randomIp)
NameError: name 'randomIp' is not defined

I don't know what's up. I have the global put into tutorial() and it doesn't have an error for saying randomIp isn't defined in the command global randomIP only for print(randomIp + '.' + randomIp + '.' + randomIp + '.' + randomIp). Does anyone know what the problem is? And if I wanted a different random number to be printed after each ".". What would the code be for that? I would like it so that it would print out something like 23.321.43.23. A completely different number after each period.

Answer 1

You created a local variable, but then you try to access a global of the same name.

You could simply omit the global keyword.

def game():
    randomIp = ...
    def tutorial():
        print(randomIp + ...)

Note that this will only work if you don't assign randomIp inside tutorial(), otherwise you will need the nonlocal declaration:

def game():
    randomIp = ...
    def tutorial():
        nonlocal randomIp
        randomIp += 5 # counts as assignment
        print(randomIp + ...)

Also note that it's more typical in python to use .format() instead of + when working with strings...

# This works
print('{0}.{0}.{0}.{0}'.format(randomIp))

# This does not work
# print(randomIp + '.' + randomIp + '.' + randomIp + '.' + randomIp)

This is because you can't add an integer to a string in Python. In some other languages, this will result in automatic conversion. In Python, it will just result in an error.

Generating a random IP

This will generate a random IP address from a valid /8 block, skipping the 127 localhost block, multicast blocks, and whatnot. It may generate addresses which are broadcast addresses, depending on the netmask.

def randomIp():
    x = random.randint(1, 222)
    if x == 127:
        x += 1
    return '{}.{}.{}.{}'.format(
        x,
        random.randint(0, 255),
        random.randint(0, 255),
        random.randint(0, 255))

Of course, you shouldn't actually use the IP address for anything.