Read from a Text File

What Will You Learn
In this tutorial, you'll explore Python's file handling capabilities, focusing on reading text files. You'll learn how to open files using the open() function, read entire files or specific lines with read(), readline(), and readlines(), and manage file resources efficiently using the with statement. The guide also covers best practices for handling different file encodings and error management, equipping you with the skills to read and process text files effectively in Python.

Being able to read data from a text file is one of the most fundamental skills in Python programming. It’s essential for tasks like reading logs, configuration files, user input, and data for analysis. Whether you’re building a script to process CSV reports or parsing logs from a server, you’ll need to understand how to open and read files safely and efficiently.

Python provides a powerful set of tools for file handling that are both easy to use and flexible. Learning how to use these tools correctly — especially the with statement and file reading methods — is crucial for writing reliable and professional-quality scripts.

How to Read Data from a Text File in Python?

The most common way to read data from a file in Python is using the built-in open() function. You should always use it in combination with the with statement to ensure that the file is automatically closed. There are three main methods to read content: read() reads the entire file as one string, readline() reads one line at a time, and readlines() reads the file into a list of lines.

Below are practical examples showing how to read text from a file in Python.

    # Example 1: Read the entire file
    with open("sample.txt", "r") as file:
        content = file.read()
        print(content)

    # Example 2: Read file line by line
    with open("sample.txt", "r") as file:
        for line in file:
            print(line.strip())

    # Example 3: Read all lines into a list
    with open("sample.txt", "r") as file:
        lines = file.readlines()
        print(lines)  # ['First line\n', 'Second line\n', ...]

Understanding how to read data from a text file in Python gives you access to external content and makes your programs far more useful.

Reading Specific Content from a File

Sometimes you don’t need the entire file — just specific parts. Python makes it easy to read a particular line, word, number, or even structured data like a matrix or dictionary. This is useful when you’re working with large files or want to extract only targeted content. You can use line indexes, split(), and other built-in functions to access and parse data in a structured way. Let’s go through practical use cases.

Read a Specific Line

To read a specific line from a file, first read all lines using readlines() or convert the file into a list with list(file). Then access the desired line by its index. Remember that indexes start from 0. Also, make sure the file contains enough lines to avoid IndexError.

    with open("data.txt", "r") as file:
        lines = file.readlines()
        third_line = lines[2]  # 3rd line (index 2)
        print(third_line.strip())

Read Words or Tokens

To read individual words or tokens from a file, loop through each line and use the split() method. This breaks a string into words based on spaces by default. You can also split by commas or other delimiters for more structured files. This is useful for text parsing, keyword searches, or token-based processing.

    with open("text.txt", "r") as file:
        for line in file:
            words = line.split()
            print(words)  # ['This', 'is', 'a', 'line']

Read Numbers or Integers

If your file contains numeric data, read each line and convert the tokens into integers using int(). You can use list comprehensions to keep your code clean and efficient. Always ensure you strip whitespace and check for empty lines. This is helpful in data analysis and numerical processing tasks.

    with open("numbers.txt", "r") as file:
        for line in file:
            nums = [int(n) for n in line.strip().split()]
            print(nums)  # [1, 2, 3]

Read a Matrix (2D list)

Reading a matrix involves reading each line and splitting it into elements, then storing those lists inside a master list. This technique is widely used in competitive programming, image processing, and simulations. Each row of the file becomes one sublist in the matrix. Use int() or float() to cast values as needed.

    matrix = []
    with open("matrix.txt", "r") as file:
        for line in file:
            row = [int(n) for n in line.strip().split()]
            matrix.append(row)

    print(matrix)  # [[1, 2], [3, 4], [5, 6]]

Read a Dictionary or Key-Value Pairs

If your file contains key-value pairs (like name: John), read each line, split it by the delimiter (e.g. colon), and store the results in a dictionary. This method is useful for reading configuration files, user data, or metadata. Always strip whitespace to avoid errors and handle malformed lines safely.

    data = {}
    with open("config.txt", "r") as file:
        for line in file:
            if ":" in line:
                key, value = line.strip().split(":", 1)
                data[key.strip()] = value.strip()

    print(data)  # {'name': 'John', 'age': '30'}

Common Mistakes When Reading from Text Files in Python

Forgetting to Close the File

A frequent beginner mistake is opening a file with open() but not closing it afterward. This leads to resource leaks and file locks, especially on Windows systems. Always use the with statement, which automatically closes the file when you're done. This ensures safe and clean file handling, even if an error occurs mid-execution.

    # Wrong
    file = open("data.txt", "r")
    content = file.read()
    # file.close() is missing

    # Correct
    with open("data.txt", "r") as file:
        content = file.read()

Reading the File Multiple Times

Once a file is read using read(), the file pointer moves to the end. If you try to read it again without resetting the pointer using seek(0), you'll get an empty string. This is a common issue when beginners try to call multiple read() or readlines() in a row.

    # Wrong
    with open("file.txt", "r") as f:
        print(f.read())
        print(f.read())  # Will print nothing

    # Correct
    with open("file.txt", "r") as f:
        print(f.read())
        f.seek(0)
        print(f.read())

Ignoring Whitespace and Newlines

Beginners often forget to strip trailing newline characters when processing lines from a file. This can cause visual issues in output or problems when comparing strings. Always use strip() or rstrip() to clean up lines after reading.

    # Wrong
    with open("data.txt") as f:
        for line in f:
            print("Line:", line)  # Includes '\n'

    # Correct
    with open("data.txt") as f:
        for line in f:
            print("Line:", line.strip())

Using Wrong File Path

Another common error is trying to open a file using a wrong or relative path. This leads to FileNotFoundError. Always check the current working directory and use absolute paths for better reliability, especially when running scripts from different locations.

    # Wrong
    open("data.txt", "r")  # Fails if file not in same directory

    # Correct
    open("/absolute/path/to/data.txt", "r")

Treating All Content as Strings

File content is read as strings by default. Beginners often forget to convert strings to numbers before performing arithmetic operations. This leads to type errors or incorrect logic. Use int() or float() to safely convert data after reading.

    # Wrong
    with open("nums.txt") as f:
        for line in f:
            total = line + 10  # TypeError

    # Correct
    with open("nums.txt") as f:
        for line in f:
            total = int(line.strip()) + 10

Frequently Asked Questions (FAQ)

      with open("file.txt", "r") as f:
          content = f.read()
          print(content)
      

      with open("data.txt") as f:
          all_text = f.read()
          first_line = f.readline()
          all_lines = f.readlines()
      

      with open("log.txt", "r") as file:
          for line in file:
              print(line.strip())
      

      # Safe pattern
      with open("C:/data/input.txt", "r") as file:
          print(file.read())
      

      with open("numbers.txt", "r") as file:
          for line in file:
              numbers = [int(n) for n in line.strip().split()]
              print(numbers)