Python - Working with Text Files

Working with Text Files in Python

In Python, Working with text files states reading from, writing to, and appending data in text format. Python provides built-in functions to handle text files easily using the open() function, which allows us to specify modes such as reading, writing, or appending.

There is a list of basic operations

1. Opening a File: The open() function opens a file and returns a file object.
2. Reading a File: We can read the entire content or line-by-line from the file.
3. Writing to a File: Save new content or overwrite existing content in a file.
4. Appending to a File: Add new content to the end of a file without overwriting the existing data.
5. Closing a File: It is important to close the file to free up system resources.

Reading a Text File

To read a file; We can read the entire contents of a file, read specific lines, or iterate over each line. We have the following methods that should be used when reading a file:

1. file.read(): Reads the entire content.
2. file.readline(): Reads a single line.
3. file.readlines(): Reads all lines and returns them as a list.

Example

The following is a code example of reading a text file:

# Open the file and read all content
with open('example.txt', 'r') as file:
    content = file.read()
    # Prints the entire file content
    print(content)
# Reading the file line by line
with open('example.txt', 'r') as file:
    for line in file:
        # Strip removes extra newlines
        print(line.strip())

Writing to a Text File

To write content to a file, use the 'w' mode. This will overwrite the file if it exists, or create a new file if it doesn’t. We have the following methods that should be used when writing to a file:

file.write(): Writes a string to the file.
file.writelines(): Writes a list of strings to the file.

Example

This example demonstrates the writing to a file.

# Writing to a file (overwrites existing content)
with open('output.txt', 'w') as file:
    file.write("Hello, World!\n")
    file.write("This is a new line.\n")

# Writing a list of strings to the file
lines = ["First line\n", "Second line\n", "Third line\n"]
with open('output.txt', 'w') as file:
    file.writelines(lines)

Appending to a text file

Use 'A' mode to append or add new content to an existing file without overwriting it.

Example

This example demonstrates how we can append new content to an existing file.

# Appending to an existing file
with open('output.txt', 'a') as file:
    file.write("Appended line 1\n")
    file.write("Appended line 2\n")

Closing a File

It is important to close the file after processing to free up system resources. If you use the with statement (context manager), Python will automatically close the file. However, use with open() is preferred as it handles closing the file automatically.

file = open('example.txt', 'r')
# Perform file operations
# Close the file when done
file.close()