Python Debugging With pdb: Summary

Debugging in Python With pdb Austin Cepalia 01:26

Here are all of the commands you covered in this course:

p: Print the value of an expression.
pp: Pretty-print the value of an expression.
n: Continue execution until the next line in the current function is reached or it returns.
s: Execute the current line and stop at the first possible opportunity (either in a function that is called or in the current function).
c: Continue execution and only stop when a breakpoint is encountered.
unt: Continue execution until the line with a number greater than the current one is reached. With a line number argument, continue execution until a line with a number greater or equal to that is reached.
l: List source code for the current file. Without arguments, list 11 lines around the current line or continue the previous listing.
ll: List the whole source code for the current function or frame.
b: With no arguments, list all breaks. With a line number argument, set a breakpoint at this line in the current file.
w: Print a stack trace, with the most recent frame at the bottom. An arrow indicates the current frame, which determines the context of most commands.
u: Move the current frame count (default one) levels up in the stack trace (to an older frame).
d: Move the current frame count (default one) levels down in the stack trace (to a newer frame).
h: See a list of available commands.
h <topic>: Show help for a command or topic.
h pdb: Show the full pdb documentation.
q: Quit the debugger and exit.

Congratulations, you made it to the end of the course! What’s your #1 takeaway or favorite thing you learned? How are you going to put your newfound skills to use? Leave a comment in the discussion section and let us know.

00:00 We covered a lot of different commands in this course and you’ll find all of them down below the video for future reference.

00:08 In this course, we learned how to print expressions, step through code, use breakpoints, continue execution, display expressions, and see stack traces that show the path of execution up to a certain stack frame. This might seem like a lot to understand at first, especially when we have GUI-based debuggers at our disposal, but I’d encourage you to write some simple programs and try pdb for yourself.

00:39 The more you use it, the more sense it will make, and the more comfortable you’ll be with the tool.

00:46 You never know when it’ll come in handy. We also have a handy pdb Command Reference, which I recommend downloading and keeping open while you’re practicing your pdb skills.

00:59 This PDF shows you all the pdb commands you can execute, including ones not covered in this video course. It’s a great resource to have, especially when you’re just getting started with pdb.

01:12 I’ve linked that down below.

01:15 I am Austin Cepalia with realpython.com. Thanks for watching this and supporting us with your subscription. Happy coding!

robotslave on Feb. 3, 2020

Thanks for the course. Pdb is much like the Perl debugger. I have one problem though - can’t get it working with Robot. If I launch the Robot executable with Pdb, I can specify a breakpoint (at least it is not rejected) - but then pdb doesn’t seem to stop at it at all. If tends to stop where there is a Pause (Robot keyword) call in the code, and at that point all the scope that is available is the Pause keyword scope. So any variables I want to print are only from the Pause Robot keyword - completely useless. Do you have any suggestions how to make it work with Robot?

Yvonne Wilmot on Sept. 25, 2020

Thanks that was great … Love the extra pdb++ .. until I came to the pdbpp decorator @pdb.hideframe and got an error. (I’m running on Windows with Python 3.8.5 in PyCharm)

import pdb

def log_in(username):
    pdb.set_trace()
    if username != "steve":
        greet(username)
    else:
        print("steve is not welcome here")

@pdb.hideframe
def greet(name):
    print(f"Hello {name}!")

user_input = input("Enter your name: ")
log_in(user_input)

I get the following error when trying to run my program in the command line:

(venv) C:\Users\YvonneW\python\my_debugging>python example6.py
Traceback (most recent call last):
  File "example6.py", line 14, in <module>
    def greet(name):
  File "C:\Users\YvonneW\python\my_debugging\venv\lib\site-packages\pdb.py", line 1266,
in hideframe
    c = types.CodeType(
TypeError: an integer is required (got type bytes)

Did I miss something?

Austin Cepalia RP Team on Sept. 25, 2020

@Yvonne Wilmot Hmm, that code looks right to me. Judging by the stacktrace, it looks that’s an issue with PDB++. I’ve seen this TypeError a lot with modules that are incompatible with Python 3.8. Try running the script with 3.7 and see if that works.

Ghani on Oct. 25, 2020

Very informative; thanks!

stephenm on Feb. 28, 2021

Excellent tutorial! Easy to follow, clearly explained. Thank you!

tobenary on May 17, 2021

I have my company code running on docker containers. will it work there as well? also, whats the best way of printing values? ( or, I guess that we need to use logger.info(f”and then, our {value}”)

Bartosz Zaczyński RP Team on May 18, 2021

@tobenary What you need in this case is running a remote debugger. The easiest way would be to use an IDE like PyCharm, which takes care of the details. However, if you wanted to use PDB in the command-line, then that’s also possible. Google the phrase “pdb docker remote debugging”.

Omar Rizwani on Aug. 1, 2022

pdb++ is a handy little extra…

Pavneet Ghai on Oct. 25, 2022

I often check the type of variable value, is there a way to check the type of variable? Most of the time I don’t have write mode on files, I would prefer using python3 -m pdb fileName.py. can someone share video line on this please.

jankesjanco on Jan. 8, 2024

Thank you for the tutorial, I’ve learned a lot from it :)

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