how to find the middle number in python

Put them in a list, sort them, pick the middle one.

>>> x = [1,3,2]
>>> sorted(x)[len(x) // 2]
2

The fastest obvious way for three numbers

def mean3(a, b, c):
    if a <= b <= c or c <= b <= a:
        return b
    elif b <= a <= c or c <= a <= b:
        return a
    else:
        return c