2020-04
22
字典转元组
不搞复杂的，不用超纲的方法做感觉上很简单的事其实不简单。搞明白这个练习后，列表、字典、元组的相爱相杀我算是有点明白了。感谢那个我觉得过于复杂的参考答案，逼我折腾出了我自己的版本。
开心！居然习题1就用上了zip这个这章书最后才提到的大招。字典的键值对互换变得如此简单，我的脑洞又开大了。
Exercise 1: Write a function called most_frequent that takes a string and prints the letters in decreasing order of frequency. Find text samples from several different languages and see how letter frequency varies between languages. Compare your results with the tables at http://en.wikipedia.org/wiki/Letter_frequencies. Solution: http://thinkpython2.com/code/most_frequent.py.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | def most_frequent(sth): d = {} for letter in sth: # 字符串转为字符映射到频率的字典 d[letter.lower()] = d.get(letter.lower(), 0) + 1 # 大写的你给我降为小写 t = tuple(zip(d.values(), d.keys())) # 用zip互换字典的键和键值，生成元组（也可以生成列表，但生成新字典你会哭死） return sorted(t, reverse = True) # 以第一元素降序输出 sth = 'This chapter presents one more built-in type, the tuple, and then shows how lists, dictionaries, and tuples work together. I also present a useful feature for variable-length argument lists, the gather and scatter operators.' t = most_frequent(sth) for item in t: print(item) # 原汁原味输出元组好，因为空格不用''圈着都不知道那里有东西 # (33, ' ') # (25, 'e') # (23, 't') # (16, 's') # (15, 'r') # (14, 'a') # (11, 'o') # (11, 'n') # (10, 'i') # (10, 'h') # (9, 'l') # (7, 'u') # (7, 'p') # (5, ',') # (4, 'g') # (4, 'd') # (3, 'w') # (3, 'f') # (3, 'c') # (2, 'm') # (2, 'b') # (2, '.') # (2, '-') # (1, 'y') # (1, 'v') # (1, 'k') |
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