pdb is the Python debugger (others are also available!)
We generally invoke it as a script to run other scripts:
python3 -m pdb myscript.py
We can also use it to switch to debugging part way through a program by importing the pdb class and calling the set_trace() method at the location where you want to start debugging:
import pdb; pdb.set_trace()
You can then step through the code following this statement, and continue running without the debugger using the continue command.
| Command | Effect |
|---|---|
| h | Obtain help on commands |
| n | executes the next line of code (skips over subroutines) |
| s | steps into a subroutine |
| l | list lines of code. Optionally specify a range of lines (e.g. l 10,20). Otherwise will list from the current line. |
| p | print the contents of a variable (e.g. p a) |
| b | break the execution of the code at a specified line (e.g. b 32) or function (e.g. myfunc). Without arguments, list the break points |
| cl | Delete a specified breakpoint (e.g. cl 1) or all break points (cl - asks for confirmation) |
| c | continue execution until a breakpoint, or the end of the code, is reached |
| q | quit |
For more details see https://docs.python.org/3/library/pdb.html.
Try it out on this example code [example1.py].