又到 Python 作业时间，这次三道题有两道题难住了我。。。

又遇到难题了，人不在学校还没法跟同学们一块讨论，只能求助 V2EX 的各路大神了！

第一题是写一个 Function 把负面评价全部改成正面。。。还要求大小写对应还有如果提到等待时间，等待时间要减半。。。这个可咋整？

Exercise 3. You are a restaurant owner plagued by bad online reviews. You want to write a function to turn these bad reviews into good reviews. In a file called positivity.py, write a function positivize(review) that takes review text review as a string. Your function should return a “positivized” version of the review, where:

• Every instance of the word “bad” should be replaced by “good”

• Every instance of the word “horrible” should be replaced by “fantastic”

• Every instance of the word “dirty” should be replaced by “clean”

• Every instance of the word “disgusting” should be replaced by “sublime”

• Every instance of the word “expensive” should be replaced by “affordable”

• Every instance of the word “moldy” should be replaced by “flavourful”

• Every instance of the word “frozen” should be replaced by “farm-fresh”

• Every instance of the phrase “n minutes” should be replaced by “only n=2 minutes”

Your function should preserve the original review’s capitalization – i.e. “Dirty” should map to “Clean.” You can assume the original review is capitalized sensibly. Example: The string

The food was horrible!!! We waited 40 minutes for frozen vegetables and moldy bread. Disgusting!

should map to

The food was fantastic!!! We waited only 20 minutes for farm-fresh vegetables and flavourful bread. Sublime!

第二题是写一个排序的 Function，但是不能用 list.sort 和 sorted，不过这个有点思路，就是先把 list 中最小的排出来，然后摘出来，再把这个最小的从 list 里面删除，再重复操作。

Exercise 4. In a file called order.py, write a function sort(words) , which takes as an argument a list of strings words . sort should modify words so as to sort the elements in alphabetical order. Python provides some built-in functions to do this, such as list.sort and sorted – do not use these for this exercise. Your solution should only use “basic” components for its logic, such as list access, list assignments, variables, if-statements, loops. In particular, the only built-in function you may use for this exercise is len .

Example:

animals = [ ' cat ' , ' bat ' , ' zebra ' , ' fish ' , ' dog ' ]

sort(animals)

animals

[ ' bat ' , ' cat ' , ' dog ' , ' fish ' , ' zebra ' ]