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Python函数

1. Python之调用函数

print abs(100)print abs(-20)print abs(12.34)print cmp(1, 2)print cmp(2, 1)print cmp(3, 3)print int('123')print int(12.34)print str(123)print str(1.23)L = []x = 1while x <= 100:    L.append(x * x)    x = x + 1print sum(L)

2. Python之编写函数

def square_of_sum(L):    sum = 0    for x in L:        sum = sum + x * x    return sumprint square_of_sum([1, 2, 3, 4, 5])print square_of_sum([-5, 0, 5, 15, 25])

3. Python函数之返回多值

x = (-b±√(b²-4ac)) / 2aimport mathdef quadratic_equation(a, b, c):    t = math.sqrt(b * b - 4 * a * c)    return (-b + t) / (2 * a),( -b - t )/ (2 * a)print quadratic_equation(2, 3, 0)print quadratic_equation(1, -6, 5)

4. Python之递归函数

def move(n, a, b, c):    if n ==1:        print a, '-->', c        return    move(n-1, a, c, b)    print a, '-->', c    move(n-1, b, a, c)move(4, 'A', 'B', 'C')

5. Python之定义默认参数

def greet(name='world'):    print 'Hello, ' + name + '.'greet()greet('Bart')

6. Python之定义可变参数

def average(*args):    sum = 0.0    if len(args) == 0:        return sum    for x in args:        sum = sum + x    return sum / len(args)print average()print average(1, 2)print average(1, 2, 2, 3, 4)