Python file operations

Python file

File Operation Flow

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

Mode of open File

• R, read-only mode "default"

• W, write-only mode "unreadable; not exist" created; empty content;

• X, write-only mode "unreadable; not present, create, present error"

• A, append mode "readable; not present, create; append content only;"

"+" means you can read and write a file at the same time

• r+, read and write "readable, writable"

• w+, write "readable, writable"

• x+, write "readable, writable"

• A +, write "readable, writable"

"B" means to operate in bytes

• RB or R+b

• WB or W+b

• XB or W+b

• AB or A+b

Note: When opened in B, the content read is byte type, and the byte type is also required for writing

With open ("test.txt") as F can not be active to close the file, the program will automatically close the file

The point is to read and write this piece of attention

The contents of the existing file are as follows:

123456789

Somehow, it seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongueI teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I planned

Read the contents of the file by reading:

12345678910111213

#read将文件内容一次性全部读取出来>>> with open("test.txt") as f:...     print (f.read())...     Somehow, it seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongueI teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I planned

To read the contents of a file by means of ReadLine:

123456789101112131415161718192021222324252627

#readline是将文件内容一行行的读取，每执行一次读取一行>>> with open("test.txt") as f:...     flag = True...     while flag:...         line = f.readline()...         if line:...             print (line)...         else:...             flag = False...             Somehow, it seems the love I knew was always the most destructive kind  Yesterday when I was young The taste of life was sweet As rain upon my tongue I teased at life as if it were a foolish game The way the evening breeze May tease the candle flame  The thousand dreams I dreamed The splendid things I planned

To read the contents of a file by means of ReadLines:

123456789101112131415161718192021222324252627

#readlines是将整个文件内容以列表的形式读取出来>>> with open("test.txt") as f:...     print (f.readlines())...     [‘Somehow, it seems the love I knew was always the most destructive kind\n‘, ‘Yesterday when I was young\n‘, ‘The taste of life was sweet\n‘, ‘As rain upon my tongue\n‘, ‘I teased at life as if it were a foolish game\n‘, ‘The way the evening breeze\n‘, ‘May tease the candle flame\n‘, ‘The thousand dreams I dreamed\n‘, ‘The splendid things I planned\n‘]#遍历文件内容>>> with open("test.txt") as f:...     for line in f.readlines():...         print (line)...         Somehow, it seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongue I teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I planned

Traverse file Contents directly:

123456789101112131415161718192021

>>> with open("test.txt") as f:...     for line in f:...         print (line)...         Somehow, it seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongue I teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I planned

Here is the file content after opening the file in various ways after writing "Hello World"

The contents of the file after the write is opened in a r+ way (you can see that the characters in front of the file are replaced):

123456789

hello world seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongueI teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I planned

Open the contents of the file after the write operation in a w+ way (you can see that the contents are emptied and then written):

1	hello world

Open the file for read-write operation in a A + (you can see Hello World appended to the last side of the file):

123456789

Somehow, it seems the love I knew was always the most destructive kindYesterday when I was youngThe taste of life was sweetAs rain upon my tongueI teased at life as if it were a foolish gameThe way the evening breezeMay tease the candle flameThe thousand dreams I dreamedThe splendid things I plannedhello world

Python file operations