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复习Python的第二十三天

习题 24: 更多练习

本节没有什么新的东西，是一个比较长的练习

The Codes

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 # 调用secret_formula函数，返回三个值，分别赋予beans，jars，cratesbeans, 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:" # 下面的函数返回值分别对三个格式化字符print "We'd have %d beans, %d jars, and %d crates." % secret_formula(start_point)

习题25：更多更多的练习

这节比较有趣。

def break_words(stuff):     """This function will break up words for us."""     words = stuff.split(' ')     return words def sort_words(words):     """Sorts the words."""     return sorted(words) def print_first_word(words):     """Prints the first word after popping it off."""     word = words.pop(0)     print word def print_last_word(words):     """Prints the last word after popping it off."""     word = words.pop(-1)     print word def sort_sentence(sentence):     """Takes in a full sentence and returns the sorted words."""     words = break_words(sentence)     return sort_words(words) def print_first_and_last(sentence):     """Prints the first and last words of the sentence."""     words = break_words(sentence)     print_first_word(words)     print_last_word(words) def print_first_and_last_sorted(sentence):     """Sorts the words then prints the first and last one."""     words = sort_sentence(sentence)     print_first_word(words)     print_last_word(words)

本节知识：

• import的时候不用加“.py”的后缀，此时作为模块的程序文件被编译成为字节码，后缀变为“.pyc”；
• 使用ex25调用函数时用. (dot, period)调用ex25模块中的函数，如：ex25.break_words；
• 列表是一组元素的有序集合，属于序列，用[ ]引起；
• sorted()是内置的排序函数，传入可迭代对象，reverse可以选择是否翻转序列；

Help on built-in function sorted in module builtins:sorted(iterable, /, *, key=None, reverse=False)    Return a new list containing all items from the iterable in ascending order.    A custom key function can be supplied to customize the sort order, and the    reverse flag can be set to request the result in descending order.

• 错写成wrods的提示信息NameError很常见，这里不做叙述；
• pop()函数意为删除指定位置的元素并返回该元素；

Help on built-in function pop:pop(...) method of builtins.list instance    L.pop([index]) -> item -- remove and return item at index (default last).    Raises IndexError if list is empty or index is out of range.

• 帮助文档是定义函数时放在 “”” 之间的东西，一般跟在函数定义的下一行，它们也被称作 documentation comments （文档注解），我们使用help()时看到的文档就来自这里；
• from ex25 import * 会挤占命名空间，也会让人不清楚哪个函数出自哪个模块，会使程序逻辑不清晰，不建议使用。

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