Debugging
Python Tools includes integrated support for debugging multiple types of Python
applications including attaching to Python processes, evaluating Python expressions in the watch and immediate windows, and inspecting local variables, step in, out, and over statements, set the next statement, and breaking on exceptions.
Right click on your project and choose Properties (Alt+Enter). From the Debug tab, you can choose one of four debuggers:
- Standard VS Debugger for CPython
- IronPython / .Net Debugger
- Python MPI Debugger
- Django Debugger
The Standard debugger basically works just like the VS debugger. The IronPython debugger uses the .Net debugger and allows you to debug into multi-lingual .Net projects in C#, VB, F#, ... The Python MPI Debugger supports debugging across remote processes
on an HPC cluster (discussed elsewhere).
Python Tools for Visual Studio includes an interactive window for debugging your code. You can launch the window from the Debug->Windows->Python Debug Interactive menu item. The debug interactive window can be summarized as a more powerful immediate
window, letting you execute Python code against a debugged process.
The debug interactive window automatically connects to any process started in the debugger using the Standard Python launcher, or any process that is later attached using the Python Debugger.
When execution breaks into the debugger, the debug interactive window is now ready to start executing code. Note that executing code while the process is running is not allowed.
The debug interactive window supports several meta commands. All meta commands start with a $, and you can type $ or $help to get a list of the meta commands. Here are some of the most important commands.
| Command |
Arguments |
Description |
| $procs |
|
Lists the processes currently being debugged. |
| $proc |
process id |
Switches the current process to the specified process id. |
| $proc |
|
Displays the current process id. |
| $mod |
module name |
Switches the current scope to the specified module name. This can also be done using the toolbar. The active module automatically changes back to <CurrentFrame> when execution breaks into the debugger. |
| $threads |
|
Lists the threads currently being debugged. |
| $thread |
thread id |
Switches the current thread to the specified thread id. |
| $thread |
|
Displays the current thread id. |
| $where,w,bt |
|
Lists the frames for the current thread. |
| $frame |
frame id |
Switches the current frame to the specified frame id. |
| $frame |
|
Displays the current frame id. |
| $up,u |
|
Move the current frame one level up in the stack trace. |
| $down,d |
|
Move the current frame one level down in the stack trace. |
| $continue,cont,c |
|
Starts executing the program from the current statement. |
| $stepin,step,s |
|
Steps into the next function call, if possible. |
| $stepout,return,r |
|
Steps out of the current function. |
| $stepover,until,unt |
|
Steps over the next function call. |
Note that the standard debugger windows such as Processes, Threads and Call Stack are not synchronized with the debug interactive window. This means that changing the active process/thread/frame in the debug interactive window will not affect the other debugger
windows, and similarly, changing the active process/thread/frame in the other debugger windows will not affect the debug interactive window.
The debug interactive window has its own set of options, which you can access using Tools->Options->Python Tools->Debug Interactive Window. Unlike the regular Python Interactive Window, which has one instance per Python interpreter installed, there
is only one instance of the debug interactive window. It uses the Python interpreter for the process being debugged.
