Python函数(入门6)

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http://www.cnblogs.com/why168888/p/6407970.html

本文出自:【Edwin博客园】

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 = 1
while x <= 100:
    L.append(x * x)
    x = x + 1
print 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 sum
print 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)) / 2a

import math
def 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)