Python: r vs r+ mode

r : Read only mode

Read only mode. Open a file for reading. It is the default mode, by any chance if the file is not exists, this method raise I/O error.

 

When you open a file using this mode, file handle is positioned at the beginning of the file.

 

r+ : read and write mode

Read and write mode. Open the file to perform both read and write operations. By any chance if the file is not exists, this method raise I/O error.

 

This mode opens an existing file without truncating it.

 

Below table summarizes different operations performed by these access modes.

 

Operation	r	r+
Read	Yes	Yes
Write		Yes
Create
Truncate
Handle position at start	Yes	Yes
Handle position at end

 

Let’s see it with an example.

 

hello.txt

Hello World
Welcome to the world

 

read_mode_1.py

import os

file_to_read = 'hello.txt'
path = "/Users/Shared/data"

with open(os.path.join(path, file_to_read), 'r') as fp:
    lines = fp.readlines()      
    print(lines)

Output

['Hello World\n', 'Welcome to the world\n']

Let’s read and write some content to hello.txt file.

 

read_plus_mode_1.py

import os

file_to_check = 'hello.txt'
path = "/Users/Shared/data"

with open(os.path.join(path, file_to_check), 'r+') as fp:
    lines = fp.readlines() 
    print(lines)

    print("\nWriting some content to the file\n")

    # Placing the file handle to start
    fp.seek(0)
    fp.write("test 1\n")

    # Placing the file handle to start
    fp.seek(0)
    lines = fp.readlines()
    print(lines)

Output

['Hello World\n', 'Welcome to the world\n']

Writing some content to the file

['test 1\n', 'orld\n', 'Welcome to the world\n']

 

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