你離這本書第一部分的結尾已經(jīng)不遠了，你應該已經(jīng)具備了足夠的 Python 基礎知識，可以繼續(xù)學習一些編程的原理了，但你應該做更多的練習。這個練習的內(nèi)容比較長，它的目的是鍛煉你的毅力，下一個習題也差不多是這樣的，好好完成它們，做到完全正確，記得仔細檢查。

print "Let's practice everything."
print 'You\'d need to know \'bout escapes with \\ that do \n newlines and \t tabs.'

poem = """
\tThe lovely world
with logic so firmly planted
cannot discern \n the needs of love
nor comprehend passion from intuition
and requires an explanation
\n\t\twhere there is none.
"""

print "--------------"
print poem
print "--------------"

five = 10 - 2 + 3 - 6
print "This should be five: %s" % five

def secret_formula(started):
    jelly_beans = started * 500
    jars = jelly_beans / 1000
    crates = jars / 100
    return jelly_beans, jars, crates

start_point = 10000
beans, jars, crates = secret_formula(start_point)

print "With a starting point of: %d" % start_point
print "We'd have %d beans, %d jars, and %d crates." % (beans, jars, crates)

start_point = start_point / 10

print "We can also do that this way:"
print "We'd have %d beans, %d jars, and %d crates." % secret_formula(start_point)

你看到的結果

$ python ex24.py
Let's practice everything.
You'd need to know 'bout escapes with \ that do
 newlines and   tabs.
--------------

       The lovely world
with logic so firmly planted
cannot discern
 the needs of love
nor comprehend passion from intuition
and requires an explanation

              where there is none.

--------------
This should be five: 5
With a starting point of: 10000
We'd have 5000000 beans, 5000 jars, and 50 crates.
We can also do that this way:
We'd have 500000 beans, 500 jars, and 5 crates.

附加題

1.記得仔細檢查結果，從后往前倒著檢查，把代碼朗讀出來，在不清楚的位置加上注釋。 2.故意把代碼改錯，運行并檢查會發(fā)生什么樣的錯誤，并且確認你有能力改正這些錯誤。

常見問題

Q:為什么在后面你把 jelly_beans 這個變量叫做 beans?

這是函數(shù)如何工作的一部分。記住，在函數(shù)中，變量都是臨時的.當你返回一個變量的時候，你可以把它賦值給另一個變量。我只是定義了一個叫做‘beans’的新變量去接收返回值。

Q:你所說的反向閱讀代碼是什么意思?

從最后一行開始閱讀。對比你的代碼和我的是不是一樣。如果確認一樣，向上移動一行閱讀，直到你讀到腳本的第一行為止。

Q:那首詩是誰寫的？

我寫的。