1 File operation... 1

1.1 Open and close files... 1

1.1.2 open function... 1

1.2 Properties of File Objects in Files... 1

1.2.1 Attribute... 1

1.2.2 Method... 2

1.2.3 mode='xx'attribute details... 4

1.3 OS operation files... 6

1 File Operation

1.1 Open and close files

1.1.2 open function

     file = open(file_name [,mode][,buffering]

eg: file = open("test.txt",mode = 'r',encoding = 'utf-8')

Details of parameters:

file_name: File name

mode: This parameter is optional and read-only by default (r). For details, see:

https://www.runoob.com/python/python-files-io.html

Enoding: The encoding of files

How to open a file

Note: f.close() must be written at last. Close the file. You can't read it after closing.

1.2 Properties of File Objects in Files

1.2.1 Attribute

     file = open('a.txt', mode = 'r' , encoding = 'utf-8')

Close the file.close file and return true, otherwise return false

file.name returns the file name

Fle.mode returns the access mode of the opened file

1.2.2 Method

Note: When you finish writing, you must refresh it and close it.

(1) write() method:

The write() method can write any string to an open file. Note: Python characters can be binary data, not just text.

The write() method does not automatically add a newline character (' n') at the end of the string.

def test3():
    f = open("day008/day_008_txt1",mode='w',encoding="utf-8")
    f.write('Mencius moved three times, and Mencius'mother chose to be good.\n educational environment,Multiple relocations')
    #Documentation "\n" The function is to change lines. write()Method does not automatically change lines
    f.flush()  #refresh buffer
    #result = f.read() #This sentence is wrong and cannot be read, because mode='w', read-only mode
    f.close()  #Close files
test3()

(2) read() method: read a string from an open file

def test1():    # Read operation
    f = open('day008/day_008_txt' , mode = 'r',encoding='utf-8')
    result = f.read()
    print(result)
    f.close() # Be sure to remember to write close，And write it to the end.
test1()

read(n) reads n characters. If the file is not closed, it will not read when it is read, but will start reading at the last cursor. In fact, all those with'b'are processed non-text. (Contains the following)

Note: In text mode, use "r" and "w" modes without encoding and decoding. But in non-text files, such as videos, music, etc., use'wb'and'rb', because

It is impossible to operate with `w'and `r'. Actually,

(3) close() method:

The close() method of the File object refreshes any unwritten information in the buffer and closes the file so that it cannot be written again after closing.

(4) See () method: Used to move the file to read the pointer to the specified location, that is, the cursor.

Syntax: file.seek(offset[,whence])

Offset: initial offset

whence: Optional, default value is 0. Represents where to start offset; 0 represents the beginning, 1 represents the current location, and 2 represents the end of the file.

_tell(): Get the current position of the cursor

The file.tell() method returns the current location of the file, that is, the current location of the file pointer.

day008/day_008_1.txt file content
The moon of Qin shines yet over the passes of Han,
The Long March has not been returned.
But to make Longcheng fly in,
Don't teach Huma to Duyin Mountain.

def test13():
    f = open('day008/day_008_1.txt',mode='r',encoding='utf-8')
    print(f.name)#file name
    line = f.readline()#Read a row of data in a file
    print('The data read is:%s'%(line))

    #Get the current file location
    path = f.tell()
    print('Current position:%d'%path)
    f.close()#Close files
test13()

Result:

_truncate(): truncate files

The file. truncate ([size]) method is used to truncate a file. If there is an optional parameter size, it means that the truncated file is size characters. If no size is specified, it is truncated from the current position; after truncation, all characters after size are deleted.

Note: deeping-bug: In r + mode, if you read the content, no matter how much you read, how many cursors are displayed. Rewriting or manipulating files is done at the end.

1.2.3 mode='xx'attribute details

1) a or ab:

def test4():    # a or ab For file appending, add new content after existing content
    f = open("day008/day_008_txt1", mode='a', encoding="utf-8")
    f.write("'<The Three-Character Classic:'Mother Ximeng, Choose Neighborhood'")
    f.flush()
    f.close()



def test5():    # w + Writing and Reading (Not often used) Direct coverage
    f = open("day008/day_008_txt1", mode='w+', encoding="utf-8")
    f.write("ah")
    f.flush()
    f.close()


def test6():    # a+ Additional reading
    # a+ Write before read and write after read are not able to get content, not cover.
    f = open("day008/day_008_txt1", mode='a+', encoding="utf-8")
    f.write("Learning and Learning")
    print(f.read())
    f.flush()
    f.close()

1.3 OS operation file

File modification: read the contents of the old file into memory; modify; delete the old file; replace the old file name with the new file name

Disadvantage: Memory overflows easily. Solution: read line by line, change line by line

     for line in file

 1 import os
 2 #Method 1
 3 def test10():
 4     #Open the file and create a new file
 5     with open("day008/day_008_1.txt",mode='r',encoding='utf-8') as f1,\
 6         open("day008/day_008_1_new.txt",mode='w',encoding='utf-8') as f2:
 7 
 8         content = f1.read()
 9         new_content = content.replace('Flying generals','Li Guang') # replace content
10         f2.write(new_content)   # write to f2 in
11     os.remove('day008/day_008_1.txt') #delete original file
12     os.rename('day008/day_008_1_new.txt','A life without a marquis.txt') #
13 
14 # Method 2
15 def test11():
16     f1 = open("day008/day_008_1.txt", mode='r', encoding='utf-8')
17     f2 = open("day008/day_008_1_new.txt", mode='w', encoding='utf-8')
18     for line in f1: #One line, one line, one line
19         new_line = line.replace('Li Guang','Flying generals')
20         f2.write(new_line)
21     os.remove('day008/day_008_1.txt')
22     os.rename('day008/day_008_1_new','Li Guang's Characteristic Shou')
23     f2.flush()