def isitIn(char, aStr):
    if aStr == '':
        return False
m = aStr[len(aStr) // 2]
if char == m:
    return True
elif len(aStr) == 1:
    return False
elif char < m:
    return isitIn(char, aStr[:len(aStr) // 2])
elif char > m:
    pass
Using a recursive bisection algorithm to check if character is in string