procedural generation - How can I add biomes to my generated world?

I need a way to generate a world realistically. I want to generate worlds similar to dwarf fortress.

My current code for world generation is this:

    worldTiles = ['^',',','.','.']
    def generateWorld(self, x=40, y=20):
        world = []

        for i in range(y):
            row = []

            for z in range(x):
                row.append(random.choice(self.worldTiles))

            world.append(row)
        return world

with the worlds it generates being this:

The world is ok, however what I want is biomes, not just completly random generation.

In case it helps, heres how the current generation works:

A variable called worldTiles has alls the tiles the world can have. This is used by the function. The function, creates an array, and appends a row to it. The row is then added to the world, as another array.

A example world might be:

  [
    ['^', ',', '^'],
    ['^', ',', '.'],
    ['^', ''., '.']
  ]