Python file operations

Python implements the operation of the file:

You need to open a file before reading it:

fileobj = open (filename, mode)

Explanation of the Open () call parameter:

* Fileobj is the file object returned by open ();

* filename is the string name of the file;

* Mode is a string that indicates the file type and operation

Mode:

* R Read-only mode (default)

* W Write-only mode (unreadable, non-existent, newly created; Overwrite new content if present;)

* A append mode (readable, non-existent then newly created; only append content;)

"+" means reading and writing a file at the same time:

* r+ can read and write files (readable; writable; can be appended)

* w+ Write Read

* A + with a

* b stands for binary files

Eg: Write a file

Conten = "Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested. "

Fout = open ("File.txt", "W")
Fout.write (Conten)
Fout.close ()

If the source string is larger, the data can be chunked until all characters are written:

Fout = open ("File.txt", "W")
size = Len (conten)
Offset = 0
Chunk = 100
While True:
    If offset > Size:
        Break
    Fout.write (Conten[offset:offset+chunk])
    Offset + = Chunk
Fout.close ()

Use Read (), ReadLine (), ReadLines () reading the file:

The read () function without parameters reads all the contents of the file at one time, noting that 2G files use the same size memory when they are read into the file

Fin = open ("file.txt", "R")
ct = Fin.read ()
Fin.close ()
Print (CT)

You can set the maximum number of read-in characters to limit the size that the read () function returns at one time.

ct = ""
Chunk = 100
Fin = open ("file.txt", "R")
While True:
    fragment = Fin.read (chunk)
    If not fragment:
        Break
    CT + = Fragment
Fin.close ()
Print (CT)

ReadLine () each time a line is read into the file, it is stitched into its original string by appending each line:

ct = ""
Fin = open ("file.txt", "R")
While True:
    line = Fin.readline ()
    If not line:
        Break
    CT + = line
Fin.close ()
Print (CT)
Or

Fin = open ("file.txt", "R")
While True:
    line = Fin.readline ()
    If not line:
        Break
    Print (line,end= "")
Fin.close ()

When the file read is finished, ReadLine (), read () also returns an empty string, which is sentenced to false.

The function readlines () calls each time a row is read and returns a list of single-line strings:

Fin = open ("file.txt", "R")
lines = Fin.readlines ()
Fin.close ()
For line in lines:
    Print (line, end= "")

To close a file using with automatically:

With open ("File.txt", "R") as Fin:
    While True:
        line = Fin.readline ()
        If not line:
            Break
        Print (line, end= "")

Use Seek () to change position

function tell () returns the byte offset from the beginning of the file, and the function seek () allows you to jump to the location of the other byte offset of the file, i.e. you can skip to the specified location without reading every byte of the file from the beginning

Fin = open ("file.txt", "R")
Fin.tell ()
Print (Fin.read ())
Fin.seek (10)
Print (Fin.read ())

Python file operations