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File Handling in Python

File handling is an important part of any web or desktop application. Python has several functions for creating, reading, updating, and deleting files.

The open() Function

The key function for working with files in Python is the open() function. It takes two parameters: filename and mode.

f = open("demofile.txt", "r")

File Modes

  • "r" - Read: Default value. Opens a file for reading, error if the file does not exist.
  • "a" - Append: Opens a file for appending, creates the file if it does not exist.
  • "w" - Write: Opens a file for writing, creates the file if it does not exist.
  • "x" - Create: Creates the specified file, returns an error if the file exists.
  • "t" - Text: Default value. Text mode.
  • "b" - Binary: Binary mode (e.g. images).

Reading a File

To read the content of a file, we use the read() method.

f = open("demofile.txt", "r")
print(f.read())
f.close()

Reading Parts of the File

  • read(5): Returns the first 5 characters.
  • readline(): Returns one line.
  • readlines(): Returns a list containing each line in the file.

Closing Files

It is good practice to always close the file when you are done with it.

f = open("demofile.txt", "r")
# perform operations
f.close()

The recommended way to handle files is using the with statement. It automatically closes the file for you, even if an exception is raised.

with open("demofile.txt", "r") as f:
    content = f.read()
    print(content)
# File is automatically closed here

Writing to a File

To write to an existing file, you must add a parameter to the open() function:

  • "a": Append - will append to the end of the file.
  • "w": Write - will overwrite any existing content.
with open("demofile.txt", "a") as f:
    f.write("Now the file has more content!")

Deleting a File

To delete a file, you must import the os module and use its os.remove() function.

import os


if os.path.exists("demofile.txt"):
    os.remove("demofile.txt")
else:
    print("The file does not exist")