September 11, 2024

Python Tutorials

How to Read a Text File in Python

Reading a text file in Python is a common task that can be accomplished using various methods provided by Python’s built-in functions. Below are some of the most common ways to read a text file in Python.

1. Using the open() Function

The open() function is used to open a file in Python. By default, it opens the file in read mode ('r'). You can use the read(), readline(), or readlines() methods to read the contents of the file.

2. Reading the Entire File

You can read the entire content of the file into a single string using the read() method.

Example:

# Reading the entire content of a file
with open('example.txt', 'r') as file:
    content = file.read()

print(content)

In this example, the example.txt file is opened in read mode, and its entire content is read into the content variable. The file is automatically closed when the block is exited.

3. Reading a File Line by Line

You can read a file line by line using the readline() method, which reads one line at a time, or by iterating over the file object.

Example 1: Using readline()

# Reading a file line by line using readline()
with open('example.txt', 'r') as file:
    line = file.readline()
    while line:
        print(line, end='')  # end='' prevents adding extra newlines
        line = file.readline()

Example 2: Using a for Loop

# Reading a file line by line using a for loop
with open('example.txt', 'r') as file:
    for line in file:
        print(line, end='')

In these examples, each line of the file is read and printed until the end of the file is reached. The end='' argument in the print() function prevents extra newlines from being added.

4. Reading All Lines into a List

The readlines() method reads all the lines of a file into a list, where each line is an element in the list.

Example:

# Reading all lines of a file into a list
with open('example.txt', 'r') as file:
    lines = file.readlines()

for line in lines:
    print(line, end='')

In this example, the readlines() method reads the file into a list named lines. Each line can then be processed individually.

5. Handling File Not Found Errors

It’s a good practice to handle cases where the file might not be found or other I/O errors might occur using a try-except block.

Example:

# Handling file not found errors
try:
    with open('example.txt', 'r') as file:
        content = file.read()
    print(content)
except FileNotFoundError as e:
    print(f"Error: {e}")

In this example, if the file example.txt does not exist, a FileNotFoundError will be caught and an error message will be displayed.

6. Reading a File Using pathlib

The pathlib module provides an object-oriented approach to handling file paths and reading files.

Example:

# Reading a file using pathlib
from pathlib import Path

file_path = Path('example.txt')

if file_path.exists():
    content = file_path.read_text()
    print(content)
else:
    print("File not found")

In this example, pathlib is used to check if the file exists and to read its content.

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