Debugging In Python Using IPDB

Python is a popular programming language that according to statista is the 3rd most used and 49.28% of developers use. But unlike some other languages debugging in Python can sometimes be challenging. Recently, working on a challenge I began working with IPDB which is a debugging tool that you can use to correct your code.

What is IPDB?

So what is IPDB? IPDB is an alternative to the default pdb debugger and uses the python shell environment to make debugging easier. Running your code with this program can be used in several ways entering the shell or even using a separate debug.py file, my preferred method for larger programs.

How does it Work?

By inserting the IPDB code line you can pause your code at that line and optionally enter commands to check how your code in working in real time. This provides invaluable feedback to the beginning programmer making the learning curve faster by saving much needed debugging time. Debugging in this way lets you know exactly what your code is executing step-by-step without the guesswork normally associated with python debugging.

Problems IPDB can Solve

1. Unintended Behavior.

Infinite loops, incorrect conditionals or faulty functions can all cause behavior that doesn't work as intended which can cost hours of development time that can be easily corrected.

1. Check Variable Values

One aspect of coding that can frustrate even experienced developer is variables that don't have the values you expect them to. IPDB when running simply allows you to type the variable in the terminal to view its contents.

1. Check Loops and Recursions

Loops and recursion often give erratic behavior and are the cause of many code gremlins. By incrementally going thru code you can see where the errors are and correct them.

1. Exception Tracking

When exceptions are raised it can be difficult to see where and IPDB can inform you when the exception is raised. This makes tracking what is throwing them much easier lowering developer stress levels.

IPDB in Action

There are several ways to set up IPDB but the most straightforward way is to start with an in program import and break point.

Here is a simple example of this in the following code:

# import IPDB debugger
import ipdb

def add_numbers(a, b):
    # debug code line
    ipdb.set_trace()  # Start debugging from this point
    result = a + b
    return result

x = 5
y = 10
print(add_numbers(x, y))

By running our program in the terminal with the ipdb.set_trace() code we will enter the IPDB program in the terminal. In this example we see that before the addition of 2 numbers we are stopping the program which will give us the insight we need to see what is going on in our code.

In the next example we can see how IPDB can be used in a loop.

import ipdb

def calculate_square(n):
    return n * n

def main():
    numbers = [1, 2, 3, 4, 5]
    squared_numbers = []

    for num in numbers:
        # debug code line
        ipdb.set_trace()  # Start debugging at each iteration
        squared_numbers.append(calculate_square(num))

    print("Original numbers:", numbers)
    print("Squared numbers:", squared_numbers)

As you can see we put ipdb.set_trace() in our code line giving us the chance to increment through our code to see the updated values in our variables.

In both examples you can see IPDB in action and using it can be a easy as entering these commands:

• n or next: Execute the current line and stop at the next line in the same function.
• s or step: Step into functions called from the current line.
• c or continue: Continue execution until the next breakpoint or program termination.
• q or quit: Exit the debugger and terminate the program.

In these examples IPDB is a simple but powerful but offers insight into our code so that we don't spend hours guessing on how we can fix it. Instead we can just use IPDB to understand what our code is doing. IPDB is user friendly, easy to use and learn, so no more excuses start using it today and get rid of few more code gremlins.