Can Python generate a random number that excludes a set of numbers, without using recursion?

Question

I looked over Python Docs (I may have misunderstood), but I didn't see that there was a way to do this (look below) without calling a recursive function.
What I'd like to do is generate a random value which excludes values in the middle.

In other words,
Let's imagine I wanted X to be a random number that's not in
range(a - b, a + b)
Can I do this on the first pass,
or
1. Do I have to constantly generate a number,
2. Check if in range(),
3. Wash rinse ?

As for why I don't wish to write a recursive function,
1. it 'feels like' I should not have to
2. the set of numbers I'm doing this for could actually end up being quite large, and
... I hear stack overflows are bad, and I might just be being overly cautious in doing this.

I'm sure that there's a nice, Pythonic, non-recursive way to do it.

Answer 1

Generate one random number and map it onto your desired ranges of numbers.

If you wanted to generate an integer between 1-4 or 7-10, excluding 5 and 6, you might:

1. Generate a random integer in the range 1-8
2. If the random number is greater than 4, add 2 to the result.

The mapping becomes:

Random number:    1  2  3  4  5  6  7  8
Result:           1  2  3  4  7  8  9 10

Doing it this way, you never need to "re-roll". The above example is for integers, but it can also be applied to floats.