習題 19: 函數(shù)和變量

函數(shù)這個概念也許承載了太多的信息量，不過別擔心。只要堅持做這些練習，對照上個練習中的檢查點檢查一遍這次的聯(lián)系，你最終會明白這些內(nèi)容的。

有一個你可能沒有注意到的細節(jié)，我們現(xiàn)在強調(diào)一下：函數(shù)里邊的變量和腳本里邊的變量之間是沒有連接的。下面的這個練習可以讓你對這一點有更多的思考：

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)

通過這個練習，你看到我們給我們的函數(shù) cheese_and_crackers 很多的參數(shù)，然后在函數(shù)里把它們打印出來。我們可以在函數(shù)里用變量名，我們可以在函數(shù)里做運算，我們甚至可以將變量和運算結(jié)合起來。

從一方面來說，函數(shù)的參數(shù)和我們的生成變量時用的 = 賦值符類似。事實上，如果一個物件你可以用 = 將其命名，你通常也可以將其作為參數(shù)傳遞給一個函數(shù)。

你應該看到的結(jié)果

你應該研究一下腳本的輸出，和你想象的結(jié)果對比一下看有什么不同。

$ python ex19.py
We can just give the function numbers directly:
You have 20 cheeses!
You have 30 boxes of crackers!
Man that's enough for a party!
Get a blanket.

OR, we can use variables from our script:
You have 10 cheeses!
You have 50 boxes of crackers!
Man that's enough for a party!
Get a blanket.

We can even do math inside too:
You have 30 cheeses!
You have 11 boxes of crackers!
Man that's enough for a party!
Get a blanket.

And we can combine the two, variables and math:
You have 110 cheeses!
You have 1050 boxes of crackers!
Man that's enough for a party!
Get a blanket.
$

加分習題

1. 倒著將腳本讀完，在每一行上面添加一行注解，說明這行的作用。
2. 從最后一行開始，倒著閱讀每一行，讀出所有的重要字符來。
3. 自己編至少一個函數(shù)出來，然后用10種方法運行這個函數(shù)。