File processing (b)

File processing (b)

File Handling

What is file: the concept of virtual storage operating system provides a letter (to store information in binary)

What is file handling: modify the stored information

Operating procedures:

1. open a file

   print('D:\上海python12期视频\python12期视频\day 09\test.py')
   print('D:\上海python12期视频\python12期视频\day 09\\test.py') # \\t--》第一个\会让第二个\失去意义
   print(r'D:\上海python12期视频\python12期视频\day 09\test.py') # r会让内部所有的\失效

2. Modify / read files

   f.write('''
   孩儿立志出湘关，学不成名誓不还
   埋骨何须桑之地，人生无处不青山
   ''')

3. save document

   f.flush() # 快速保存，你可以不使用

4. Close the file

   f.close # 告诉操作系统关闭文件

The three file Open

1. Read

   # 读取：rt   read_text 读文本内容，只读，不可修改
   f =open(r'D:\上海python12期视频\python12期视频\day 09\test.py', 'rt', encoding='utf8')
   

2. Write

    # wt：只写(w清空文件后写入)，不可读
   f = open(r'D:\上海python12期视频\python12期视频\day 09\test.py', 'wt', encoding='utf8')
   

3. Additional writing

   # at:只写入(追加写入)
   f = open(r'D:\上海python12期视频\python12期视频\day 09\test.py', 'at', encoding='utf8')
   f.write('中')

   Open the file in two ways:

   t ---> text

   b ----> binary mode: The two things that are not used alone, with r / w / a in combination with, no encoding

   b mode is generally used for picture / audio / video save

Absolute and relative paths

Absolute path: from the beginning of the letter D: \ Shanghai python12 of video \ python12 of video \ day 09 \ test.py

Relative path: file name of the executable file (currently running file) files, executable files and open files that belong to the same file

Try to use a relative path

f = open('test.py','r',encoding='utf8')
print(f.read())

with file management context

with: providing an automatic shut down file (the lifting of the occupation of the operating system)

with pen('text.py','r',encoding='utf8') as f:
    date = f.read   # data放到python的内存中
    
print(date)
# 关闭文件(操作系统),没有关闭python内存中的文件

Advanced application file

Three new models:

1. Readable and writable: r +

   with open('text.py','r+',encoding='utf8')
    fr.write('高级')  # 光标在文件头部，覆盖后面的字符

2. Readable and writable: w + w and not make any difference

   with open('text.py','w+',encoding='utf8')
    fr.write('高级')  # 先清空后写入

3. Readable and writable: a + a default mode at the end of the cursor

   with open('text.py','a+',encoding='utf8')
    print(fr.read())    # 光标在文件末尾，所以显示为空

4. File modification

   # 同时打开多个文件
   # (1)
   with open（'test.py', 'r', encoding='utf8') as fr, \
            open('test_swap.py', 'w', encoding='utf8') as fw:
   
       date = fr.read()
       date= date.replace('sb','bs')
   
       fw.write(date)
   
   
   # (2)
   with open('test.py', 'r', encoding='utf8') as fr, \
            open('test_swap.py', 'w', encoding='utf8') as fw:
        # 再大的文件都能修改
        for i in fr:
            s = '傻逼'
            i = i.replace('sb', s)
            fw.write(i)
            fw.flush()  # 先保存成功再继续运行