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4.6. Debugging

What is software debugging?

Software debugging is the process of identifying, analyzing, and fixing bugs or errors in a software program. It involves running the program in a controlled environment, where you can inspect variables, step through code, set breakpoints, and understand the program's execution flow to find where things are going wrong.

Why is software debugging important?

Debugging is crucial for several reasons:

  1. Ensures Code Correctness: It helps ensure that the software behaves as expected and meets its requirements.
  2. Improves Code Quality: Through debugging, developers can identify and correct underlying issues that might not be immediately apparent, leading to more robust and error-free code.
  3. Saves Time and Resources: Debugging can be a more efficient way to diagnose and fix problems compared to manually scrutinizing code or relying on scattered print statements. It allows for a systematic examination of the program’s execution.

Compared to print statements, debugging offers a quicker and more interactive alternative. You don't have to add print statements, execute your program, and then remove those statements. Instead, you can insert breakpoints and examine the code as much as you want without restarting the program.

What is the benefit of debugging over logging?

While logging provides valuable insights, especially in a production environment, debugging is a more dynamic tool during development to understand code behavior.

The two approaches are complementary:

  • Logging offers initial insights about code execution, helping to pinpoint where issues might occur.
  • Debugging allows for an in-depth investigation of these issues through breakpoints and real-time inspection, without the need for code execution to complete.

Which tool should you use to debug your code?

Python includes pdb (Python Debugger), a powerful but command-line-based tool that can be challenging for those not comfortable with CLI environments.

For a more user-friendly experience, Integrated Development Environments (IDEs) like Visual Studio Code (VS Code) offer integrated debugging tools. These tools provide a graphical interface for debugging, making it easier to set breakpoints, step through code, and inspect variables.

How should you debug your code with VS Code?

To start debugging in VS Code, follow these steps:

  1. Set a Breakpoint: Click to the left of the line number where you want the execution to pause. A red dot appears, indicating a breakpoint.
  2. Launch the Debugger: Open the Run and Debug sidebar (Ctrl+Shift+D on Windows/Linux, Cmd+Shift+D on macOS) and start a debugging session by selecting the appropriate configuration for your project and clicking the green play button.
  3. Control Execution: Use the debugging control panel to step over (execute the current line), step into (dive into functions called on the current line), or continue (resume execution until the next breakpoint or the end of the program).
  4. Inspect Variables: Hover over variables in the editor to see their current values. The Debug Sidebar also provides a comprehensive view of variables in scope.

Additionally, you can use the Debug Console to execute commands and modify variables on the fly, offering an interactive environment to test fixes or understand behavior without altering the source code directly.

What are some tips for improving your debugging experience?

To enhance your debugging experience, consider the following tips:

  • Use Conditional Breakpoints: Instead of stopping at every iteration of a loop, you can set conditions for breakpoints to pause execution only when certain conditions are met, saving time.
  • Leverage Watch Expressions: Add expressions or variables to the watch list to monitor their values in real-time, helping to quickly identify when and how they change unexpectedly.
  • Understand the Call Stack: The call stack shows you the path execution took to get to the current point. Analyzing it can help identify how different parts of the code interact and where errors propagate from.
  • Experiment in the Debug Console: Use the debug console to test potential fixes or understand complex code behavior without needing to modify and rerun your program.
  • Familiarize Yourself with Debugger Features: Spend time learning the features and shortcuts provided by your IDE's debugger. Efficiency in debugging often comes from knowing how to quickly navigate and use available tools.

Mastering the debugger and incorporating these practices can significantly improve your efficiency in diagnosing and fixing issues, making the debugging process less daunting and more productive.

Debugging additional resources