The basics of Python Learn the operation of the Nineth day file

1, file operation

Parameters: 1, File path 2, encoding mode, 3, performing action (open mode), read only, write-only, read-write, append and read-write.

1 Open the file, get the file handle and assign a value to a variable. 2. Manipulate the file through a handle. 3. Close the file.

f = open ('yuyu', encoding='gbk', mode='R '  = f.read () print (s) f.close ()

Open is the system feature of Windows, and the default encoding for Windows is Gbk,linux operating system defaults to Utf-8.

Process: Opens a file, generates a handle, operates on a file handle, and then closes.

READ: R read-only

1, what encoding the file is stored in what encoding is opened.

2, File path: Absolute path, starting from the root directory first level lookup until found.

Relative paths, write files directly under the same folder.

Five different ways:

1,f.read, read them all. Read-only mode, can not be noted. The default is read-only mode.

F=open (' Yu.bak ', encoding= ' utf-8 ')

2,f.readline, a row of reads.

3,f.readlines reads each line of the original file as an element of a list.

4,f.read (n) is read by character in R mode. n= (number of characters)

In RB mode read (n) reads in bytes. RB mode is read-only with bytes type, non-text class file with RB

5, Loop read. This is best, and takes up less memory.

f = open ('yu','r', encoding='utf-8'  ) for in F:    print(I.strip ()) F.close ()

Write: W,write write mode

f = open ('yu','w', encoding='utf-8') = F.write (' when the moon has ')print(s) f.close ()   

W write mode, no files when creating a file to write content, there is a file, the original file content is emptied, and then write the content.

#1. The mode of opening the file has (default is text mode):R, read-only mode "default mode, the file must exist, does not exist" throw exception "W, write-only mode" is not readable; "A, append write mode is not readable;

F=open ('yu.bak', mode='rb') s= F.read (6) Print (s) f.close () #b ' alex\xe6\x98 '

Wbab Note: When opened in B, read the content is byte type, write also need to provide byte type, can not specify the encoding # #, ' + ' mode (is added a function) r+, read and write "readable, can write" w+, write read "writable, readable" A +, write read "writable, readable" # 4, read/write, read, write, read r+b, read and write "readable, writable" w+b, write read "writable, readable" a+b, write read "writable, readable" by bytes type operation

　　

1. When the file is opened in text mode, the representation reads 3 characters

2. When the file is opened in B mode, the delegate reads 3 bytes

The rest of the files within the cursor movement are in bytes such as:seek,tell,truncate

Attention:

1. Seek has three modes of movement 0,1,2, of which 1 and 2 must be performed in B mode, but regardless of which mode is moved in bytes units

2. Truncate is a truncated file, so the file must be opened in a way that can be written, but not with W or w+, etc., because the file is directly emptied, so truncate to r+ or a or a + and other modes to test the effect.

f = open ('yu','r+', encoding='utf-8') = f.truncate (4)print(s) f.close () 

2. Modification of files

#① Create a new file
#② read an original file
#③ the contents of the original file in the way you want to make changes and write to the new file
#④ Delete the original file
#⑤ Renaming a new file

With statement:

1, function One automatically closes the file handle. 2. Operate multiple files at once.

# Import OS # with open (' Yu ', encoding= ' Utf-8 ') as f1,\ #      Open (' Yu.bak ', encoding= ' utf ', mode= ' W ') as F2:#     content = F1.read ()#      new_content = content.replace (' SB ', ' Alex ')#     f2.write (new_content) # os.remove (' Yu ')

The basics of Python Learn the operation of the Nineth day file