Google python course basic exercise——mimic
在学习了前面python课程的综合知识后,再来做个小游戏。
游戏规则:任给一个文件file,实现一个dict,key为file中出现的单词,value为一个由key在file中出现的位置后紧跟的下一个单词组成的list。
例如:file中,紧跟单词'and'后可能出现了'then','the','you'等,则dict中包含{'and',['then','the','you']}。
详细描述如下:
"""Mimic pyquick exercise -- optional extra exercise. Google's Python Class Read in the file specified on the command line. Do a simple split() on whitespace to obtain all the words in the file. Rather than read the file line by line, it's easier to read it into one giant string and split it once. Build a "mimic" dict that maps each word that appears in the file to a list of all the words that immediately follow that word in the file. The list of words can be be in any order and should include duplicates. So for example the key "and" might have the list ["then", "best", "then", "after", ...] listing all the words which came after "and" in the text. We'll say that the empty string is what comes before the first word in the file. With the mimic dict, it's fairly easy to emit random text that mimics the original. Print a word, then look up what words might come next and pick one at random as the next work. Use the empty string as the first word to prime things. If we ever get stuck with a word that is not in the dict, go back to the empty string to keep things moving. Note: the standard python module 'random' includes a random.choice(list) method which picks a random element from a non-empty list. For fun, feed your program to itself as input. Could work on getting it to put in linebreaks around 70 columns, so the output looks better. """
两代码对比:
1 import random 2 import sys 3 4 5 """Returns mimic dict mapping each word to list of words that follow it.""" 6 def mimic_dict(filename): 7 dict1 = {} 8 f = open(filename,'r') 9 text = (f.read()).split() 10 f.close() # a good habit to keep consistency 11 global c #to bring the value to print_mimic() function 12 c = text[0] 13 for i in range(len(text)-1): 14 if text[i] in dict1.keys(): 15 dict1[text[i]] += [text[i+1]]#append other words to existing key 16 else: 17 dict1[text[i]] = [text[i+1]] #create new elment 18 return dict1 19 20 21 """Given mimic dict and start word, prints 200 random words.""" 22 def print_mimic(mimic_dict, word): 23 for i in range(200): 24 if word not in mimic_dict.keys():#If word not in the dict, 25 #back to the empty string 26 word = '' 27 if word == '': 28 mimic_dict[word] = [c] 29 word = c 30 else: 31 word = random.choice(mimic_dict[word]) 32 #to use random.choice() to help choose 33 print word, #keep the good format 34 35 36 # Provided main(), calls mimic_dict() and mimic() 37 def main(): 38 if len(sys.argv) != 2: 39 print 'usage: ./mimic.py file-to-read' 40 sys.exit(1) 41 42 dict = mimic_dict(sys.argv[1]) 43 print_mimic(dict, '') 44 45 46 if __name__ == '__main__': 47 main()
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1 import random 2 import sys 3 def mimic_dict(filename): 4 """Returns mimic dict mapping each word to list of words which follow it.""" 5 # +++your code here+++ 6 # LAB(begin solution) 7 mimic_dict = {} 8 f = open(filename, 'r') 9 text = f.read() 10 f.close() 11 words = text.split() 12 prev = '' 13 for word in words: 14 if not prev in mimic_dict: 15 mimic_dict[prev] = [word] 16 else: 17 mimic_dict[prev].append(word) 18 # Could write as: mimic_dict[prev] = mimic_dict.get(prev, []) + [word] 19 # It's one line, but not totally satisfying. 20 prev = word 21 return mimic_dict 22 # LAB(replace solution) 23 # return 24 # LAB(end solution) 25 26 def print_mimic(mimic_dict, word): 27 """Given mimic dict and start word, prints 200 random words.""" 28 # +++your code here+++ 29 # LAB(begin solution) 30 for unused_i in range(200): 31 print word, 32 nexts = mimic_dict.get(word) # Returns None if not found 33 if not nexts: 34 nexts = mimic_dict[''] # Fallback to '' if not found 35 word = random.choice(nexts) 36 # The 'unused_' prefix turns off the lint warning about the unused variable. 37 # LAB(replace solution) 38 # return 39 # LAB(end solution) 40 41 # Provided main(), calls mimic_dict() and mimic() 42 def main(): 43 if len(sys.argv) != 2: 44 print 'usage: ./mimic.py file-to-read' 45 sys.exit(1) 46 47 dict = mimic_dict(sys.argv[1]) 48 print_mimic(dict, '') 49 50 51 if __name__ == '__main__': 52 main() |
运行结果示意:
PS:
- 表格左边一列是我刚开始学小试牛刀时写的一小段代码,右边是后来查看google提供的anwser。两段代码均能实现功能,逻辑基本一致,前者可读性略差于后者,稍显冗余啦啦,学习了。
- 本题旨在帮助熟悉文本分割,提取文本内容,掌握random.option()等函数使用,帮助分析词汇前后相关性,提高搜索性能。
转载于:https://www.cnblogs.com/Emma437211/archive/2013/04/03/2997432.html