10  Python File Handling

Python allows us to read, write, create and delete files. This process is called file handling.

10.0.1 The open() function

The open() function allows us to read, create and update files

It takes 2 parameters:

  • file - the file or file path to be opened
  • mode - the mode in which a file is opened for

The mode is a string that can either be any of the following:

Mode Meaning
'r' Open a file for reading
'w' Open a file for writing, creates the file if it does not exist
'a' Open a file for writing, appends to the end of the file
'x' Open a file for creating, fails if file already exists

10.1 Python File reading

To better explain this, let us say we have a folder named my_folder.

Inside my_folder we have the following files:

  • demo.txt
  • main_code.py

The content of the demo.txt file is the following

Hello World!
I love Python

Now our goal is to read the content of the demo.txt file and then print it using the main_code.py file

To achieve this, we will use the open() function with 'r' mode.

# this is main code

file = open(
    file='demo.txt',
    mode='r'
)
content = file.read()
print(content)
Hello World!
I love Python

10.1.1 Reading Lines

We can also read each line using the readline() method.

# this is main_code.py

file = open(
    file='demo.txt',
    mode='r'
)

first_line = file.readline()
second_line = file.readline()

print('First line:', first_line)
print('Second line:', second_line)
First line: Hello World!

Second line: I love Python

10.2 Writing a File

In simplest terms, writing a file means modifying the content of a file or creating it if it doesnot exist yet.

In Python, there are 2 modes to write to file.

  • 'w' - overwrites content of a file, creates file if it does not exist
  • 'a' - appends content to the end of a file, creates the file if it does not exist

Example To better explain this, lets say we have a folder named my_folder. Inside my_folder we have the following files

  • demo.txt
  • main_code.py

The content of the demo.txt file is the following

I love Python

In this example, we will use the 'w' mode which will overwrite(replace) the content of the file

# this is main_code.py

file = open(
    file='demo.txt',
    mode='w'
)
file.write('I love JavaScript')
file.close()

When the above code is run, the content of the file demo.txt will be this:

I love JavaScript

Another example, this time we will use the a mode which will append or add content to the end of the file

# this is main_code.py

file = open(
    file='demo.txt',
    mode='a'
)
file.write(' and JavaScript')
file.close()

When the above script is run, the content of the demo.txt file will be this:

I love Python and JavaScript

10.3 Deleting a file

To delete a file, use the os module. The os modules contains the remove() method which we can use to delete files.

# this is main_code.py

# import os

# os.remove('demo.txt')