teste.py

#coding:utf-8
#!/usr/bin/env python
values = []
total = None

def is_max(a, b):
    return a >= b

def is_min(a, b):
    return a <= b

def get_max(numbers):
    out = 0

    for number in numbers:
        if is_min(out, number):
            out = number

    return out

def get_min(numbers):
    out = numbers[0] or 0

    for number in numbers:
        if is_max(out, number):
            out = number

    return out

while True:
    number = input("\nInsira um numero: ")
    values.append(number)
    pass_away = raw_input("\nContinuar inserindo? ")

    if not pass_away == "S":
        break;

total = len(values)

print '-' * 25
print 'Lista de valores: \n %s' % (values)
print 'Valor máximo: \n %s' % (get_max(values))
print 'Valor minimo: \n %s' % (get_min(values))