sketch.txt为两个人的对话内容。文本格式为
角色：台词
以下源码的功能是分解sketch.txt的每一行，将角色和台词根据冒号分解成两部分，形成
角色 said ： 台词
的格式重新输出。
data = open("sketch.txt")
for each_line in data:
role, content = each_line.split(":")
print "%s said: %s" % (role, content)
data.close()
执行程序时，出现以下异常：
Man said: You didn't!
Other Man said: I'm telling you, I did!
Man said: You did not!
Other Man said: Oh I'm sorry, is this a five minute argument, or the full halfhour?
Man said: Ah! (taking out his wallet and paying) Just the five minutes.
Other Man said: Just the five minutes. Thank you.
Other Man said: Anyway, I did.
Man said: You most certainly did not!
Traceback (most recent call last): File "file.py", line 21, inrole, line_spoken = each_line.split(":")
ValueError: too many values to unpack
从以上输出可以看到，程序在分解到“Man said: You most certainly did not!”的下一行时出现ValueError异常。
所以自然想到这一行的下一行是什么呢？
打开sketch.txt，可以发现是下面这一行：
Other Man: Now let's get one thing quite clear: I most definitely told you!
仔细观察，这一行有两个冒号，这样的话split(":")会将这一行分解成三部分，但代码中并没有处理这第三部分的代码，所以ValueError提示值过多。
发现了问题那就好解决了，只需为split函数设置一个分割次数的参数就可以了。
role, content = each_line.split(":", 1)
看执行结果：
依然有个ValueError异常，但仔细观察，这已经不是上面那个ValueError，而是一个新的异常
Other Man said: Oh yes I did!
Man said: Oh look, this isn't an argument!
Traceback (most recent call last): File "file.py", line 24, inrole, line_spoken = each_line.split(":", 1)
ValueError: need more than 1 value to unpack
再次打开sketch.txt文档，查看“Man said: Oh look, this isn't an argument!”的下一行：
(pause)
这一行没有一个冒号，所以split()会出现异常。
发现问题解决问题，跳过这种提示行
修改代码：
data = open("sketch.txt")
for each_line in data:
if each_line.find(":") < 0:
print each_line
continue
else:
role, line_spoken = each_line.split(":", 1)
print "%s said: %s" % (role,line_spoken)
data.close()
find()函数找不到冒号，返回-1，所以代码会跳出本次循环，执行下一次循环。
这样处理后，程序执行时不再异常。
（也许有更好异常的处理方式）
