p18,19 函数

函数 print_two 的问题是：它并不是创建函数最简单的方法。在 Python 函数中我们可以跳过整个参数解包的过程，直接使用 () 里边的名称作为变量名。这就是 print_two_again 实现的功能。

接下来的例子是 print_one ，它向你演示了函数如何接受单个参数。

最后一个例子是 print_none ，它向你演示了函数可以不接收任何参数。

# this one is like your scripts with argv
def print_two(*args):
    arg1, arg2 = args
    print "arg1: %r, arg2: %r" % (arg1, arg2)

# ok, that *args is actually pointless, we can just do this
def print_two_again(arg1, arg2):
    print "arg1: %r, arg2: %r" % (arg1, arg2)

# this just takes one argument
def print_one(arg1):
    print "arg1: %r" % arg1

# this one takes no arguments
def print_none():
    print "I got nothin'."


print_two("Zed","Shaw")
print_two_again("Zed","Shaw")
print_one("First!")
print_none()
 

*args 的 *是什么意思？它的功能是告诉 python 让它把函数的所有参数都接受进来，然后放到名字叫 args 的列表中去。和你一直在用的 argv 差不多，只不过前者是用在函数上面。没什么特殊情况，我们一般不会经常用到这个东西。

def cheese_and_crackers(cheese_count, boxes_of_crackers):
    print "You have %d cheeses!" % cheese_count
    print "You have %d boxes of crackers!" % boxes_of_crackers
    print "Man that's enough for a party!"
    print "Get a blanket.\n"


print "We can just give the function numbers directly:"
cheese_and_crackers(20, 30)


print "OR, we can use variables from our script:"
amount_of_cheese = 10
amount_of_crackers = 50

cheese_and_crackers(amount_of_cheese, amount_of_crackers)


print "We can even do math inside too:"
cheese_and_crackers(10 + 20, 5 + 6)


print "And we can combine the two, variables and math:"
cheese_and_crackers(amount_of_cheese + 100, amount_of_crackers + 1000)