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Python Debugging With pdb: Summary

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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.

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!

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