Python: 字典应用题

Write a program to read through the mbox-short.txt and figure out who has sent the greatest number of mail messages. The program looks for 'From ' lines and takes the second word of those lines as the person who sent the mail. The program creates a Python dictionary that maps the sender's mail address to a count of the number of times they appear in the file. After the dictionary is produced, the program reads through the dictionary using a maximum loop to find the most prolific committer.

name = input("Enter file:")
if len(name) < 1 : name = "mbox-short.txt"
handle = open(name)
counts = dict()
persons = list()
clist = list

for line in handle:
    line = line.rstrip()
    clist = line.split()
#Guardian pattern
    if line == '':
        continue
    if clist[0] is 'From':
        persons.append(clist[1])
for person in persons:
    counts[person] = counts.get(person,0) +1

bigcount = None
bigperson = None
for p,c in counts.items():
    if bigcount is None or c>bigcount:
        bigcount = c
        bigperson = p

print(bigperson, bigcount)

python 数据结构综合题：

1. 每一个代码块都实现一个功能，功能之间不要冗杂：
2. 以行为单位读文件
3. .split() 把string拆成一个list, 如果list首元素为From，则把list[2]拿出来，存到新列表person list里面
4. 用dictionary做histogram，把（key, value）是（人名，次数）
5. 遍历 dictionary，找最大值

这样，功能分布清晰，提高代码可读性，也有利于debug

Guardian pattern:

防止line是空行，否则closet[0] 会报错: out of range. 因为是空list，没有list[0]元素

有个很好的debug教程：

Python data structures - week 4 - Assignment Chapter 8 - Worked exercise ( 看助教是怎么找错的～