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How to Build a Python Script: A Beginner’s Guide to Python Scripting

Learn scripting and how to build Python scripts from scratch. Set up your environment, structure your code, run the script, and explore real examples with tips to get started.

What is a Python script?

Scripting refers to writing small programs called “scripts” to automate tasks, manipulate data, or control other programs. A Python script is a .py file containing a sequence of instructions in the Python programming language that are executed line by line by an interpreter.

Unlike compiled languages (such as C++ or Java), which require code to be transformed into machine language before running, scripting languages like Python are interpreted directly. This makes them ideal for quick development and automation.

Benefits of scripts:

  • Automation: Scripts are great for automating repetitive tasks like renaming files, scraping data, or sending emails.
  • Simplicity: Scripts are often easier to write, understand, and modify than full-scale applications.
  • Flexibility: You can quickly test and run parts of your code without compiling it.

Think of scripting as giving your computer a to-do list—and Python is the language you use to write that list.

Now that we understand scripting and why it’s useful, let’s prepare our system to write and run Python scripts.

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Setting up the environment to create a Python script

Before writing our first Python script, we need a few tools in place: Python, a code editor, and a space to store the project.

Install Python

Python needs to be installed on our computer to run scripts. If you haven’t installed it, follow our step-by-step instructions on the Installing Python 3 and Python Packages article.

Install Visual Studio Code

While we can use any text editor to write scripts, a dedicated code editor like Visual Studio Code (VS Code) makes it easier with features like syntax highlighting and debugging tools. Check out our Getting Started with Visual Studio Code article to get started.

Create a project folder and script file

Once Python and the editor are ready, it’s time to organize our workspace:

  • Create a Folder: Make a new folder for your Python projects on your computer. You can name it something like python-scripts.

  • Create a Python File: Inside this new folder, create a file and name it something like rename_files.py.

Here’s an example of what our folder structure should look like 

python-scripts/ 
├── rename_files.py      # Your main Python script file 
└── README.md            # Optional: A file to describe your project

We’re just about ready to start writing our scripts, but before we dive in, let’s go over the basic structure of a script.

Structure of a Python script

Before diving into writing the code, it’s essential to understand the basic structure of a Python script. A well-organized script will be easier to write, debug, and maintain.

Inserting the shebang line

You can add a shebang at the top of your script on Unix-based systems like macOS or Linux. The shebang tells the system which interpreter to use when running the script.

Example: 

#!/usr/bin/env python3

This line is optional for Windows users, but it’s a good practice to include it if you’re working in a cross-platform environment.

Importing modules

Python allows us to import pre-written code (called modules) to extend the functionality of our script. These can be built-in Python modules or external libraries you’ve installed.

For example, if we want to work with dates and times, we can import the datetime module: 

import datetime

We can also import specific functions from a module: 

from datetime import datetime

Defining functions

Functions organize our code into reusable blocks. In Python, functions are defined using the def keyword.

Example: 

def greet(name): 
  return f"Hello, {name}!"

Main program block

In Python, it’s common to include a special if __name__ == "__main__": block to run our script only when executed directly, not when imported as a module into another script.

Example: 

if __name__ == "__main__": 
  print("This script is running directly!")

Code execution

Once we’ve written the code, we can run the script from our terminal or editor. The code inside the if __name__ == "__main__": block will execute when the script is run directly.

This structure is the foundation of most Python scripts. Let’s build our first Python script by combining all these concepts in an example!

Building our first Python script

Let us build a Python script that automates a task: renaming files in a folder. This script will allow us to quickly rename multiple files with a standardized naming pattern, saving time and effort. Open the rename_files.py file we had created earlier, and paste this code into it: 

import os 


# This function renames all files in the given folder using a consistent naming pattern 
def rename_files_in_directory(directory, name_prefix="renamed_file", file_extension=".txt"):  
  try:  
    files = os.listdir(directory) # Get all files in the directory 
    for i, filename in enumerate(files): 
      new_name = f"{name_prefix}_{i+1}{file_extension}"    # Create a new name 
      old_path = os.path.join(directory, filename)         # Full path to the original file 
      new_path = os.path.join(directory, new_name)         # Full path to the new file 
      os.rename(old_path, new_path)                        # Rename the file 
      print(f"Renamed: {filename} -> {new_name}") 
 
  except FileNotFoundError: 
    print("Directory not found. Please check the path.") 
 
  except Exception as e: 
    print(f"An error occurred: {e}") 
  
# Main program block - this runs only when the script is executed directly 
 if __name__ == "__main__":  
   folder_path = "your/folder/path/here"     # Replace with your actual folder path 
   rename_files_in_directory(folder_path)

In this script:

  • We import the os module to work with folders and files on your computer.
  • The function rename_files_in_directory():
    • Takes a folder path.
    • Loops through all the files in it.
    • Renames each file using a pattern like renamed_file_1.txt, renamed_file_2.txt, etc.
  • The main block at the bottom runs the function only when we run the script directly.

We need to update the folder path, save the file, and run the script to rename our files.

Now that we’ve built our first Python script, let’s walk through how to run a Python script from the terminal or code editor.

How to run a Python script?

Once you’ve written and saved your script, it’s time to execute it. Here’s how you can run a Python script in a few ways:

Run the Python script from the terminal

To run the Python script using the terminal, follow the steps as mentioned:

  • Open terminal (command prompt or shell) and navigate to your project folder
  • Use the cd command to move into the folder where your .py file is saved:
cd path/to/your/project-folder
  • Run the Python script using this command:
python rename_files.py

Note: Use python or python3 depending on your setup.

Run the Python script on Visual Studio Code

To run the Python script on Visual Studio Code, click on the run button at the top right, or use the shortcut keys:

On windows: Ctrl + F5

On macOS: Cmd + F5

We’ll see the output in the Terminal panel at the bottom.

Once the script runs, it will rename all the files in the target folder, and we’ll see messages printed for each renamed file.

We’ve built and successfully run our first Python script! Next, explore a few best practices to help us write better Python scripts.

Best practices for writing Python scripts

Whether working on a small task or building something big, following good practices makes our code easier to understand, debug, and share. Here is a list of some of them:

Use meaningful variable and function names

Avoid using vague names like x or temp (unless appropriate). Instead, choose names that describe what the value or function does. Instead of creating a function as follows: 

def fn(a): 
  return a * a

Create a function with an understandable name: 

def square_number(number): 
  return number * number

Add comments and docstrings

Use comments to explain complex or essential parts of your code. Add docstrings at the beginning of functions to describe what they do and what arguments they expect. 

# Calculates the area of a rectangle  
def calculate_area(length, width):  
  """Returns the area given length and width."""  
  return length * width

Follow the PEP 8 style guide

PEP 8 is Python’s official style guide. It covers:

  • Naming conventions
  • Indentation (4 spaces)
  • Line length (max 79 characters)
  • Spacing and blank lines

Most code editors like VS Code highlight PEP 8 issues automatically.

Organize code into functions or modules

Break large scripts into smaller functions to avoid repetition. For very long scripts, consider splitting the code across multiple modules (files) and importing them. 

# In utils.py 
def greet(name):  
  return f"Hello, {name}!" 


# In main.py 
from utils import greet  
print(greet("Alice"))

Following these practices early in the learning journey builds a strong foundation for writing clean and maintainable code, essential for individual projects and team-based development.

Conclusion

In this article, we explored how to build Python scripts from scratch. From understanding what scripting means, setting up the environment, writing and running a script, to learning best practices, each step helps build confidence and clarity in automating tasks with Python.

To expand your knowledge of Python’s core concepts like variables, functions, and control flow, check out the Learn Python 3 course on Codecademy. It’s a great next step to strengthen your skills and take on more advanced scripting projects.

Frequently asked questions

1. How do I compile a Python script?

You don’t need to manually compile Python scripts like in other programming languages. Python is an interpreted language, which means you just run the script using the command: 

python script_name.py

2. What is the Python script format?

A Python script is a plain text file with a .py extension. It contains Python code written using proper indentation and syntax. A typical script might include:

  • Imports
  • Functions
  • Conditional statements
  • A main block (if __name__ == "__main__":)

3. Is Python a scripting language?

Yes, Python is considered a scripting language because it’s often used to automate tasks, write small programs, and quickly build prototypes. It’s also a general-purpose programming language used for web development, data science, AI, and more.

4. What is __init__ in Python?

__init__ is a special method in Python classes. It runs automatically when a new object is created and is used to initialize the object’s attributes.

5. What is the main() function in Python?

Python doesn’t require a main() function like other languages, but defining one for clarity is a common practice. The standard way to run the main logic is: 

if __name__ == "__main__":  
  main()

This block ensures your script runs only directly executed, not when imported as a module.

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