What Is A Breakpoint In Python? Complete Guide

Breakpoints in Python are an essential tool for debugging your code. They allow you to pause the execution of your program at a specific point so that you can examine the state of your variables and understand why your code is behaving in a certain way.

In this blog post, we’ll discuss how to use breakpoints in Python and provide some examples to illustrate the concept.

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How To Use Breakpoints In Python

The built-in ‘pdb‘ library in Python provides functionality for working with breakpoints. You can use the ‘pdb.set_trace()‘ function to set a breakpoint in your code. When the execution reaches that line, the program will pause and drop into the interactive pdb debugger. Then, you may analyze the program’s state and progress through the code by using various commands.

Here’s an example of using ‘pdb.set_trace()’ to set a breakpoint in a simple Python script:

import pdb

def my_function():

x = 1

y = 2

pdb.set_trace() # this line sets a breakpoint

z = x + y

print(z)

my_function()

When you run this script, the execution will pause at the line with pdb.set_trace(). You’ll land into the pdb prompt, where you can use commands like ‘n‘ (next) and ‘s‘ (step) to step through the code and ‘p‘ (print) to examine the values of variables.

Alternatively, you can use the built-in python breakpoint() function, which is more concise and works from Python 3.7.

def my_function():

x = 1

y = 2

breakpoint() # this line sets a breakpoint

z = x + y

print(z)

my_function()

Using an IDE like PyCharm, you can set breakpoints in Python by clicking on the line number on the left side of the editor window, and a red dot will appear, which indicates the breakpoint.

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Use Of Breakpoints In Python

• Breakpoints can be very useful in several situations. For example, if you’re trying to track down a bug in your code, you can set breakpoints at strategic points and step through the code to see how it affects the variables.

• Additionally, you can use breakpoints to pause the execution of a script and examine the state of your variables when it meets a specific condition. For example, you might set a breakpoint inside a loop and examine the value of a variable after a certain number of iterations.

• Breakpoints can also temporarily halt the execution of a script and investigate the state of the program. For example, if you have a script that is running too long or seems to be stuck in an infinite loop, you can set a breakpoint to pause the execution and investigate the state of the program.

• You can also use conditional breakpoints, where the execution of the program halts only when it meets a specific condition. This is especially handy when tracking down a bug that only appears under certain conditions. For example, you should set a breakpoint that only hits when a particular variable has a certain value or when a specific function is called.

• In addition to the pdb library, many IDEs and text editors have built-in support for breakpoints. For example, PyCharm, a popular Python IDE, has a dedicated “Debug” mode that allows you to set breakpoints, step through the code, and examine the program’s state in a user-friendly interface. Similarly, Visual Studio Code and Sublime Text are text editors that can set breakpoints and debug your code.

Points To Remember When Using Breakpoints In Python

When using breakpoints, it’s essential to remember that breakpoints can slow down the execution of your script. This can make it complex and challenging to see the overall behavior of the program. To mitigate this, you can use the continue command in the pdb prompt to continue the execution of the script until the next breakpoint. This can help you quickly navigate the script section you are interested in investigating.

Another consideration to keep in mind is using breakpoints with production systems. You want to ensure that there are no breakpoints left behind when you run the final version of your script. It’s best practice to remove all breakpoints before deploying to production or use a script to disable them before deploying.

Conclusion

Breakpoints are a powerful debugging tool in Python, and they’re easy to use with the built-in pdb library. By setting breakpoints and stepping through your code, you can better understand how your code is behaving and quickly identify and fix any bugs that might be present.

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