Detailed explanation of Python3 file operations

Steps of file operation:

Open file-> Operate file->Close file

Remember: Close the file at the end (otherwise there may be unexpected results)

Open file

File handle = open('file path', 'mode')

Specify file encoding

File handle = open ('file path','mode',encoding='utf-8')

In order to prevent forgetting to close the file, you can use the context manager to open the file

with open('file path ', 'mode') as file handle:

The modes for opening files are:

r, read-only mode (default).

w, write-only mode. [Unreadable; create if it does not exist; delete content if it exists;]

a, append mode. [Readable; if it does not exist, create it; if it exists, only append the content;]

r+, the file can be read and written. [Readable; Writable; Appendable]

w+, write and read

"U" means that \r \n \r\n can be automatically converted to \n when reading (Same as r or r+ mode)

rU

r+U

"b" means processing binary files (such as: FTP sendingupload ISO image file, linux can be ignored, windows needs to be marked when processing binary files)

rb

wb

ab

Close File

File handle.close()

Operation file:

detach

#Placeholder

fileno (returns the file descriptor, used for I/O operations of the underlying operating system)

fid = file handle.fileno()

print(fid)

flush (Refresh the buffer and write the data in the buffer to the file immediately)

File handle.flush()

isatty (Judge the file Whether to connect to a terminal device, return a Boolean value)

File handle.isatty()

read (read the specified number of characters from the file, read all by default)

str = file handle.read() #Read the entire file

str1 = file handle.read(10) #Read the first 10 characters of the file

readable (determine whether the file is readable, return a Boolean value)

File handle.readable()

readline (Read at most one line of data at a time, the end of each line Contains newline character '\n')

print(file handle.readline()) #Read the first line of data

print(file handle.readline(3)) #Read the first line of data The first 3 characters of the second line

print(file handle.readline()) #Read the remaining characters of the second line

print(file handle.readline()) #Read the third line

seek (Move the pointer for file reading. If the file contains Chinese characters, the moving pointer must be a multiple of 3, otherwise an error will be reported, because one Chinese character is equal to 3 bytes)

File Handle.seek(6)

seekable (determine whether the file pointer is available, return a Boolean value)

File handle.seekable()

tell (get the pointer position)

File handle.tell()

truncate (truncate, delete the content behind the pointer and write it to the file, operate in writable mode)

f = open( 'text.txt','r+',encoding='utf-8')

f.seek(9) #Move the pointer to the end of the 9th byte (that is, after the 3rd Chinese character)

f.truncate() #Delete the characters after the third Chinese character and write it to the file

f.close()

writable (determine whether the file is writable, Returns a Boolean value)

File handle.writable()

write (Write string to the file and return the number of characters)

File handle .write('string')

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