Python(3):文件读写与异常

 1 # 假设我在 /home/zyq/KiDe/Python/test 文件夹中有一个文件 test.txt 那么我可以通过以下命    令定位到该文件夹：
 2 >>>import os
 3 >>>os.chdir('/home/zyq/KiDe/Python/test')
 4 # 此时可以通过 os.getcwd() 来得到当前的工作目录。 
 5 # 此时可以通过如果下命令来进行文件读取测试：
 6 >>>data = open('test.txt')        
 7 >>>print(data.readline(), end='')
 8 This is line1
 9 >>>print(data.readline(), end='')
10 This is line2
11 >>>data.seek(0)                        # 此时将游标又放到了文件最开始
12 >>> for each_line in data:    
13         print(each_line, end='')
14 >>>data.close()                        # 一定要记得关闭读取流

 1 Man: You didn't!
 2 Other Man:I'm telling you, I did!
 3 Man: You did not!
 4 Other Man:Oh I'am sorry, is this a five minute argument,or the full of the half hour?
 5 Man:Ah!(taking out his wallet and paying) Just the five minutes.
 6 Other Man:Just the five minutes. Thank you.
 7 Other Man:Anyway, I did.
 8 Man:You most certainly did not!
 9 Other Man:Now let's get one thing quite clear:I most definitely old you!
10 Pause
11 Man:Oh no you didn't!
12 Other Man: Oh yes I did!
13 End

1 >>>for each_line in data:
2 >>>    (role, line_spoke) = each_line.split(":", 1)
3 >>>    print(role, end='')
4 >>>    print(" says: ", end='')
5 >>>    print(line_spoke, end='') 

 1 # 方案一： 使用 each_line.find(":")来判断当前行中是否有分割符
 2 >>>for each_line in data:
 3 >>>    if not each_line.find(":") == -1:
 4 >>>        print(role, end='')
 5 >>>           print(" says: ", end='')
 6 >>>        print(line_spoke, end='')
 7 # 这个方案不强壮且可能需要经常变动。此时可以用到异常：
 8 # 方案二： 使用try except来处理，对于异常处理如果使用pass的话表示忽略这个异常继续执行：
 9 >>>for each_line in data:
10 >>>    try:
11 >>>        print(role, end='')
12 >>>           print(" says: ", end='')
13 >>>        print(line_spoke, end='')        
14 >>>    except:
15 >>>        pass 

 1 try:
 2     data = open('test3.txt')
 3     for each_line in data:
 4         (role, line_spoken) = each_line.split(":", 1)
 5         print(role, end='')
 6         print(" says: ", end='')
 7         print(line_spoken, end='')
 8 except ValueError：
 9     pass 　　　　　　　　　　# 表示忽略该异常，程序继续往下运行
10 except IOError:
11     print("File not exists!")
12 finally:
13     if 'data' in locals():                # 判断data变量是否存在当前区域内
14         print("Close file!")
15         data.close() 

 1 import os
 2 os.chdir('/home/zyq/KiDe/Python/test')
 3 man = []
 4 otherMan = []
 5 try:
 6     data = open('test2.txt')
 7     for each_line in data:
 8         (role, line_spoken) = each_line.split(":", 1)
 9         #print(role, end='')
10         # Store the message to array by the man
11         line_spoken = line_spoken.strip()
12         if role == 'Man':
13             man.append(line_spoken)
14         else:
15             otherMan.append(line_spoken)  
16         #print(" says: ", end='')
17         #print(line_spoken, end='')
18 except ValueError:
19     pass
20 except IOError:
21     print("File not exists!")
22 finally:                            # 必定会执行的
23     if 'data' in locals():      # 判断data变量是否存在，即是否打开了文件流
24         print("Close file test2.txt!")
25         data.close()
26  
27 #write two arrays to file
28 try:
29     out1 = open("man.txt", "w")
30     out2 = open("otherMan.txt", "w")
31     
32     print(man, file = out1)
33     print(otherMan, file = out2)
34 
35 except IOError:
36     print("File write error!")
37 finally:
38     out1.close()
39     print("Close file man.txt!")
40     out2.close()
41     print("Close file otherMan.txt!")  

 1 import os
 2 os.chdir('/home/zyq/KiDe/Python/test')
 3 man = []
 4 otherMan = []
 5 try:
 6     with open('test2.txt') as data:           # with打开的不需要显示的关闭
 7         for each_line in data:
 8             (role, line_spoken) = each_line.split(":", 1)
 9             # Store the message to array by the man
10             line_spoken = line_spoken.strip()
11             if role == 'Man':
12                 man.append(line_spoken)
13             else:
14                 otherMan.append(line_spoken)  
15 except ValueError:
16     pass
17 except IOError as err:
18     print("File read error:" + str(err))        # 输出具体异常信息
19  
20 #write two arrays to file
21 try:
22     with open("man.txt", "w") as out1, open("otherMan.txt", "w") as out2:
23         print(man, file = out1)
24         print(otherMan, file = out2)
25 except IOError as err:
26     print("File write error:" + str(err)) 

 1 import os
 2 import pickle
 3 os.chdir('/home/zyq/KiDe/Python/test')
 4 man = []
 5 otherMan = []
 6 try:
 7     with open('test2.txt') as data:
 8         for each_line in data:
 9             (role, line_spoken) = each_line.split(":", 1)
10             # Store the message to array by the man
11             line_spoken = line_spoken.strip()
12             if role == 'Man':
13                 man.append(line_spoken)
14             else:
15                 otherMan.append(line_spoken)  
16 except ValueError:
17     pass
18 except IOError as err:
19     print("File read error:" + str(err))
20  
21 #write two arrays to file
22 try:
23     with open("man.txt", "wb") as out1, open("otherMan.txt", "wb") as out2:
24         pickle.dump(man, file = out1)
25         pickle.dump(otherMan, file = out2)
26 except IOError as err:
27     print("File write error:" + str(err))
28  
29 # 此时如果想读取man.txt文件中的信息的话，只需使用：
30 import pickle
31 with open('man.txt', 'rb') as data:
32     list = pickle.load(data)
33 # 此时list就是原来的列表。可以直接通过list[0]、list[1] 等来访问列表中的对应项。