Generate a random character not found in another string

Question

I have a string which has some chars and I need to generate a random uppercase char which is not found in my string.

Example: str = "SABXT" The random char can be any char which is not in str

I tried:

string.letters = "SABXT"
random.choice(string.letters)

but this do the opposite, it generates the char from my str

Answer 1

Get a list of characters that are not in your string, and then use random.choice to return one of them.

import string
import random

p = list(set(string.ascii_uppercase) - set('SAXBT'))
c = random.choice(p)

Granted, the subsequent random.choice may seem redundant since the set shuffles the order, but you can't really depend on the set order for randomness.

Answer 2

import string,random
prohibitted = "SABXT" 

print random.choice(list(set(string.ascii_uppercase)-set(prohibitted)))

Is one way.

Another might be:

import string,random
prohibitted = "SABXT" 
my_choice = random.randint(0,26)
while char(ord('A')+my_choice) in prohibitted:
    my_choice = random.randint(0,26)
print char(ord('A')+my_choice)

Yet another way might be:

import string,random
my_choice = random.choice(string.ascii_uppercase)
while my_choice in prohibitted:
    my_choice = random.choice(string.ascii_uppercase)