breakpoint() function in Python

Introduction

While writing Python code, you will often need to debug the code. There are several tools such as debuggers and linters available but Python itself has a built-in function for this purpose called breakpoint().

The breakpoint() function was introduced in Python 3.7 version. Before its introduction, we used to use a Python module called Python Debugger. It has to be imported and then called upon as below:

import pdb
pdb.set_trace()

But with the introduction of breakpoint() function, we can call on it inside the script we want to debug without having to import any new modules.

The syntax of breakpoint() function is:

breakpoint(*args, **kws)

where *args and **kws are option arguments and keyword arguments respectively.

List of Commands

There are various commands you can use while debugging. Some of them are:

h: Help
w: where
n: next
s: step (step into the function)
c: continue
p: print
l: list
q: quit

Once you’ve finished debugging your code you can type "c" to continue and exit Python’s Debugger module.

Examples

Let us take an example of a function to find the maximum in a list.

def find_max(nums):
    maxm = 0
    for num in nums:
        breakpoint()
        if num > maxm:
            maxm = num

    return maxm

nums = [12, 45, 76, 11, 90]
print(find_max(nums))

When you run the function, you get this output:

The breakpoint() function opens the Python debugger in the console. Let us see how we can debug the function.

The debugger opens at the step: if num > maxm. So, when we used the n command, it shows the next step, i.e., maxm = num. At this stage, the value of maxm will obviously be 0. The c command is used to continue the loop. After we run c, the value of maxm is changed.

Conclusion

In this part, we learned about the Python breakpoint() function with the help of examples. There are more advanced usage of this function which is beyond the scope of this article.