python文件及异常

参与的函数
split（）
strip（）
find（）
语法：
try ：
excpt
finally

with
参与的模块
os

sketch.txt文件内容:

Man: Is this the right room for an argument?
Other Man: I've told you once.
Man: No you haven't!
Other Man: Yes I have.
Man: When?
Other Man: Just now.
Man: No you didn't!
Other Man: Yes I did!
Man: You didn't!
Other Man: I'm telling you, I did!
Man: You did not!
Other Man: Oh I'm sorry, is this a five minute argument, or the full half hour?
Man: Ah! (taking out his wallet and paying) Just the five minutes.
Other Man: Just the five minutes. Thank you.
Other Man: Anyway, I did.
Man: You most certainly did not!
Other Man: Now let's get one thing quite clear: I most definitely told you!
Man: Oh no you didn't!
Other Man: Oh yes I did!
Man: Oh no you didn't!
Other Man: Oh yes I did!
Man: Oh look, this isn't an argument!
(pause)
Other Man: Yes it is!
Man: No it isn't!
(pause)
Man: It's just contradiction!
Other Man: No it isn't!
Man: It IS!
Other Man: It is NOT!
Man: You just contradicted me!
Other Man: No I didn't!
Man: You DID!
Other Man: No no no!
Man: You did just then!
Other Man: Nonsense!
Man: (exasperated) Oh, this is futile!!
(pause)
Other Man: No it isn't!
Man: Yes it is!

先查看当前工作目录

import os
os.getcwd()   #查看当前工作目录
os.chdir(r'C:\user\......') #定位到想要去的文件中（r的作用使\不被转义）
try:
	with open('sketch.txt') as date:  #打开文件赋给date，如果出现异常关闭文件
		for each_line in date:
			try:
				(role,line_spoken) = each_line.split(':',1) #碰见:号则分裂成列表，后面的1就只分裂一次，然后给前面的 role 和line_spoken
				if(role == 'Man'):
					line_spoken = line_spoken.strip()  #去掉字符串首位的空白字符和空格
					man.append(line_spoken)  #添加到列表中
				elif(role == 'Other Man'):
					line_spoken = line_spoken.strip()
					other.append(line_spoken)
			except ValueError:  主要是判断文件中不符合标准的字符串就直接跳过
				pass
except IOError as err:
	print('File error' + str(err))  出现异常则是文件

或者：
try:           #检测到打开文件异常就抛出 The。。。并且关闭文件
    date = open('sketch.txt')
    for each_line in date:
        try:	#和上面一样，中间出现出现不符合格式的就抛出异常
            (role, line_spoken) = each_line.split(':', 1)
            line_spoken = line_spoken.strip()
            if (role == 'Man'):
                man.append(line_spoken)
            elif (role == 'Other Man'):
                other.append(line_spoken)
        except ValueError:
            pass
    date.close()   #做完了之后关闭文件
except IOError:
    print('The datefile is missing!')
finally:
    date.close()

这里展示with的作用

>>> try:
	with open('man_date.txt','w') as man_file,open('other_date.txt','w') as other_file:
		print(man,file = man_file)
		print(other,file = other.file)#这里打错了
except IOError as err:
	print('File error'+str(err))

	
Traceback (most recent call last):
  File "<pyshell#89>", line 4, in <module>
    print(other,file = other.file)#这里显示了
AttributeError: 'list' object has no attribute 'file'
抛出异常，因为other_file打错成了other.file，检查文件中发现 man_date中文件正常打印出来了
但是other_date中却是空的文件，这就显示出了with的作用，出现异常 man_file和other_file都被关闭了，但是man_file已经输出到文件了