Every programmer has to know how to debug their code, and Python provides a variety of tools and ways to do this. Learning how to efficiently debug may help you create better code and save you time and frustration whether you're a novice or an experienced developer.
We'll go through some of the essential ideas and resources you need to be familiar with to debug your Python code in this blog.
Understanding error messages
Debugging begins with analyzing error messages. Python will output a message to the console if your code makes an error and it will explain what went wrong. These signals might be obscure and challenging to decipher, especially for novices, but they include important information that can guide you in determining the error's root cause.
Take the case when your code has a syntax problem. Python will output a message that resembles this:
File "myfile.py", line 3
print('Hello, world!'
^
SyntaxError: unexpected EOF while parsing
This message tells you that there is a syntax error on line 3 of your file. The caret symbol (^) indicates where Python encountered the error. In this case, the error is a missing closing parenthesis in the print statement.
Take the time to read and understand error messages. They can be your best friend when it comes to debugging.
Using print statements
Using print statements to output numbers or messages to the console is another helpful debugging approach. This might assist you in following the logic of your programme and locating any problems.
Let's take the example of a function that isn't returning the desired result. To output the intermediate values of variables and identify the issue, utilise print
def add_numbers(a, b):
print(f'a: {a}')
print(f'b: {b}')
result = a + b
print(f'result: {result}')
return result
x = add_numbers(2, 3)
print(x)
In this example, we use print statements to output the values of a, b, and result at various points in the function. This can help us see if the function is working correctly and where any errors might be occurring.
Using a debugger
While print statements are helpful, adding and removing them from your code may be time-consuming and tiresome. Using a debugger is a more effective method of debugging.
An integrated debugger for Python is called pdb. You may use this debugger to walk through your code line-by-line, check the values of variables, and even change the values of variables as you go.
You must import the pdb debugger and add a line to your code that starts the debugger before you can use it. For instance:
def add_numbers(a, b):
result = a + b
#import pdb pdb.set_trace() use it if python version is below 3.7
breakpoint()
return result
x = add_numbers(2, 3)
print(x)
When the pdb.set_trace() / breakpoint line is executed, and the program will pause and start the debugger. You can then step through the code using various commands, such as n (next line), s (step into function), and c (continue until the next breakpoint).
Using an IDE / Editor
Debugging can also benefit from an Integrated Development Environment (IDE), which is a potent tool. Code highlighting, auto-completion, and syntax checking are features that many IDEs provide that can assist you in writing cleaner, error-free code.
Several IDEs also provide built-in debugging features that let you step through your code, look at variables, and create breakpoints. This
Debugging using vs code
Visual Studio Code (VS Code) is a popular text editor that is widely used by developers to write and debug code. In this blog, we'll cover some of the key features and techniques you can use to debug Python code on VS Code.
- Installing the Python extension
Before you can start debugging Python code on VS Code, you need to install the Python extension. This extension provides a range of features, including code highlighting, auto-completion, and debugging tools.
To install the Python extension, open VS Code and go to the Extensions panel (you can access it from the sidebar on the left or by pressing Ctrl+Shift+X). Search for "Python" in the search bar, select the "Python" extension from the list of results, and click "Install".
- Setting up a launch configuration
Once you have installed the Python extension, you need to set up a launch configuration to tell VS Code how to run your Python code in debug mode.
To set up a launch configuration, go to the Debug panel (you can access it from the sidebar on the left or by pressing Ctrl+Shift+D). Click the gear icon to open the launch.json file, and select "Python" as the environment.
You can then configure various options, such as the path to the Python interpreter, the working directory, and any arguments or environment variables you want to pass to your script.
- Adding breakpoints
Breakpoints are a key feature of debugging, as they allow you to pause your program at specific points and examine the state of your code.
To add a breakpoint in VS Code, simply click on the line number in the editor where you want to pause your program. A red circle will appear, indicating that a breakpoint has been set.
You can add as many breakpoints as you like, and you can also configure various options, such as whether to stop on exceptions or only on specific conditions.
- Stepping through code
Once you have set up your launch configuration and added breakpoints, you can start debugging your code.
To start debugging, click the "Run" button in the Debug panel (you can access it from the sidebar on the left or by pressing F5). This will run your code in debug mode, and your program will pause at the first breakpoint.
You can then use various commands, such as "Step Over" (to execute the current line and move to the next line), "Step Into" (to step into a function call), and "Step Out" (to step out of a function call).
You can also examine the state of your code using the Variables panel, which shows the values of all variables and expressions in the current scope.
- Debugging remotely
Finally, it's worth noting that you can also use VS Code to debug Python code running on a remote machine or in a Docker container.
To debug remotely, you need to set up a remote connection using the VS Code Remote Development extension. This extension allows you to connect to a remote machine or container and run your code in the same way as if you were running it locally.
Debugging Python code on VS Code can be a powerful and efficient way to identify and fix errors in your code. With the right setup and techniques, you can quickly track down bugs and write cleaner, more robust code.