A Complete Guide - Running Python Scripts

Last Updated: 03 Jul, 2025   
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Setting Up Your Environment

Installation of Python: Install Python from the # hello_world.py print("Hello, world!")

Comments in Python: Comments are crucial for code readability. Use # for single-line comments and ''' ''' or """ """ for multi-line comments.

# This is a single-line comment
"""
This is a multi-line comment.
Use this for documentation or explaining complex sections of your code.
"""

Indentation: Python relies on indentation to define blocks of code. Use 4 spaces per indentation level.

if True: print("This is indented.")

Variables and Data Types: Learn to work with different data types like strings, integers, floats, and more.

name = "Alice"
age = 30
height = 5.9
is_student = True

Functions: Functions encapsulate code blocks to perform specific tasks.

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

Running Scripts

Command Line Interface (CLI): Learn to run scripts from the command line.

  • Open the terminal or command prompt.
  • Navigate to the directory containing your script.
  • Run the script using python scriptname.py.
$ python hello_world.py
Hello, world!

Running in an IDE: Most IDEs provide a way to run scripts directly without opening a terminal. Look for a "Run" button or menu option.

Interactive Mode: Start Python in interactive mode to execute individual commands and test snippets.

  • Open the terminal or command prompt.
  • Type python or python3 to start the interactive shell.
$ python
>>> print("Hello, world!")
Hello, world!

Debugging and Error Handling

Syntax Errors: These occur when the interpreter encounters incorrect Python notation. Common syntax errors include missing colons or mismatched parentheses.

print("Hello, world!") # Correct
print("Hello, world!" # SyntaxError: unexpected EOF while parsing

Runtime Errors: These happen during the execution of your program. Use try-except blocks to handle exceptions gracefully.

try: x = 1 / 0
except ZeroDivisionError: print("Cannot divide by zero!")

Debugging Tools: Utilize debugging tools provided by your IDE. Breakpoints allow you to pause execution, step through code, and inspect variables.

File Handling

Reading from Files: Use Python’s built-in open() function to read data from files.

with open('example.txt', 'r') as file: content = file.read() print(content)

Writing to Files: Similarly, use open() with the w mode to write to files.

with open('example.txt', 'w') as file: file.write("This is a test.")

Appending to Files: Use the a mode to append data to existing files.

with open('example.txt', 'a') as file: file.write("\nAppending this line.")

Advanced Scripting

Modules and Packages: Organize large projects using modules and packages. Each module is a Python file, and a package is a directory containing multiple modules.

  • Import modules using the import statement.
  • For example, to use the math module:
import math
print(math.sqrt(16)) # Output: 4.0

Command-Line Arguments: Use the sys.argv list in the sys module to handle command-line arguments.

import sys
print(f"Arguments: {sys.argv}")

Virtual Environments: Isolate project dependencies using virtual environments.

  • Install virtualenv using pip install virtualenv.
  • Create a virtual environment: virtualenv venv.
  • Activate the environment:
    • On Windows: venv\Scripts\activate
    • On Unix or MacOS: source venv/bin/activate

Conclusion

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Step-by-Step Guide: How to Implement Running Python Scripts

1. Install Python

For Windows:

  1. Download Python:

  2. Run the Installer:

    • Open the downloaded .pkg file.
    • Follow the installation instructions.

  3. Verify Installation:

    • Open Terminal (you can find it in Applications > Utilities).
    • Type python3 --version and press Enter. You should see something like Python 3.x.x.

For Linux:

Ubuntu and other Debian-based systems can install Python using apt.

  1. Open Terminal.

  2. Update Package List:

    sudo apt update

  3. Install Python:

    sudo apt install python3

  4. Verify Installation:

    • Type python3 --version and press Enter. You should see something like Python 3.x.x.

2. Set Up Your Code Editor or IDE

You can use any text editor, but an Integrated Development Environment (IDE) can make things easier. Some popular ones are:

  • PyCharm: Official Python IDE by JetBrains.
  • Visual Studio Code: Lightweight editor with excellent support for Python via extensions.
  • Sublime Text: Simple and powerful editor.
  • Thonny: Good for beginners, especially with visual debugging capabilities.
  • IDLE: Comes bundled with Python.

For Visual Studio Code (VSCode):

  1. Download VSCode:

  2. Save the File:

    • Press Ctrl+S and navigate to your project folder.
    • Save the file as hello.py in your project folder.

4. Run Your Python Script

From Command Prompt/Terminal:

  • Navigate to the Project Directory:

    • Use cd command to change to the directory where your script is saved. For example: 
      cd path\to\your\project\folder # On Windows
cd path/to/your/project/folder # On macOS/Linux

  • Run the Script:

    • Type python hello.py if you're using Windows.
    • Type python3 hello.py if you're using macOS or Linux.

    When you run the command, you should see:

    Hello, World!

    printed on the screen.

From Within VSCode:

If you're using an IDE like Visual Studio Code, you don't need to navigate through directories manually.

  1. Open Your Script in VSCode.

    • Click on File > Open Folder... and select your project folder.
    • Open hello.py inside the project folder.

  2. Run the Script:

    • There are multiple ways to run a script from VSCode:
      • Using the Play Button:
        • Go to the top right corner of the editor window.
        • Click on the green play button to run the script.
      • Via Terminal:
        • Open the integrated terminal (Terminal > New Terminal).
        • Type python hello.py (or python3 hello.py) in the terminal.
      • Keyboard Shortcut:
        • Press F5 to run the script.

When you run the script, the Output panel in VSCode or your terminal should display:

Hello, World!

5. Running Python Scripts with Arguments (Optional)

Sometimes, you might need to pass arguments to your Python scripts. Let's modify our hello.py script to take name as an argument.

Steps:

  1. Modify hello.py: Replace the contents of hello.py with the following code:

    import sys def main(): if len(sys.argv) < 2: print("Hello, World!") else: print(f"Hello, {sys.argv[1]}!") if __name__ == "__main__": main()

  2. Save Changes:

    • Press Ctrl+S to save changes.

  3. Run the Script with Argument:

    • Navigate to the project directory (if not already there) in your terminal.
    • Type python hello.py John (or python3 hello.py John) and press Enter. Replace John with any name you'd like.

    Expected output:

    Hello, John!

Conclusion

Congratulations! You've completed writing and running your first Python script. Feel free to explore more by modifying the script or trying out more examples. Happy coding!

  • Variables and Data Types.
  • Control Structures (Loops, Conditionals).
  • Functions.
  • Python Libraries.
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Top 10 Interview Questions & Answers on Running Python Scripts

1. How do I run a Python script from the command line?

To run a Python script from the command line, follow these steps:

  • Open your command line interface (CLI). It’s called Terminal on macOS and Linux, Command Prompt or PowerShell on Windows.
  • Navigate to the directory containing the script using the cd command.
  • Type the following command to execute the script:
python script_name.py # On Windows/Linux
python3 script_name.py # On Linux/macOS (if multiple versions of Python are installed)

2. What is the difference between using python and python3 to run scripts?

python typically refers to Python 2.x, while python3 points to Python 3.x. Python 2.x reached its end of life in January 2020, which means it no longer receives updates or support. Most modern development and production environments use Python 3.x, so it's recommended to use python3 unless you're specifically maintaining Python 2.x code.

3. How can I make my Python script executable on Unix systems?

On Unix-based systems like Linux and macOS, you can make a Python script executable by adding a shebang line at the beginning of the file and changing the file permissions.

  • Add this line as the first line in the script:
#!/usr/bin/env python3
  • Make the script executable by running this command in your terminal:
chmod +x script_name.py
  • Now, you can run the script using ./script_name.py.

4. Can I run Python scripts directly from an IDE like PyCharm or Visual Studio Code?

Yes, IDEs provide built-in tools to run Python scripts directly without needing a command line interface.

  • In PyCharm, right-click on the script file in the Project Explorer and select "Run 'script_name'".
  • In Visual Studio Code, click on the green play button in the top-right corner of the editor, next to the Run option.

5. How do I install packages to run my script?

You can usually find required packages listed in a requirements.txt file or within the script documentation. Use pip, Python’s package installer, to install the dependencies:

  • Install all packages listed in a requirements.txt file using:
pip install -r requirements.txt
  • Install individual packages using:
pip install package_name

6. My script requires additional arguments. How do I pass them?

When running a script from the command line that expects additional arguments, type those arguments after the script name:

python script_name.py arg1 arg2

In your script, you can access these arguments using the sys.argv list from the sys module:

import sys arg1 = sys.argv[1]
arg2 = sys.argv[2] print(f"Received arguments: {arg1} and {arg2}")

Alternatively, consider using the argparse module for more sophisticated argument parsing.

7. How can I run a Python script in the background on Unix?

You can run a Python script in the background on Unix systems by appending & at the end of the command:

python script.py &

To keep the process running after closing the terminal, use nohup:

nohup python script.py &

8. Can I schedule Python scripts to run automatically?

Yes, you can use several methods to schedule tasks:

  • On Windows, use Task Scheduler.
  • On macOS/Linux, use cron jobs.

Example of setting up a cron job to run a script daily at midnight:

  • Open Terminal.
  • Type crontab -e.
  • Add the following line:
0 0 * * * /usr/bin/python3 /path/to/script.py

9. How do I run Python scripts with virtual environments?

Using a virtual environment helps manage dependencies specific to a project.

  • Create a virtual environment using:
python -m venv env_name

  • Activate the virtual environment:

    • On Windows:
    .\env_name\Scripts\activate
    • On macOS/Linux:
    source env_name/bin/activate

  • Once activated, install any necessary packages using pip inside the virtual environment.

  • To run the script, ensure the virtual environment is activated and then use the python command.

10. How can I run a Python script repeatedly or continuously?

You can run a script in a loop or continuously by incorporating a loop within the script or using external tools.

  • Inside the script, use a loop (e.g., while True) for continuous execution.
  • From the command line, use a loop (for or while) in a bash/zsh/powershell script.
  • On Unix, use watch to run a script at regular intervals:

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