I am using Python C Api to embed a python in our application. Currently when users execute their scripts, we call PyRun_SimpleString(). Which runs fine.
I would like to extend this functionality to allow users to run scripts in "Debug" mode, where like in a typical IDE, they would be allowed to set breakpointsm "watches", and generally step through their script.
I've looked at the API specs, googled for similar functionality, but did not find anything that would help much.
I did play with PyEval_SetTrace() which returns all the information I need, however, we execute the Python on the same thread as our main application and I have not found a way to "pause" python execution when the trace callback hits a line number that contains a user checked break point - and resuming the execution at a later point.
I also see that there are various "Frame" functions like PyEval_EvalFrame() but not a whole lot of places that demo the proper usage. Perhaps these are the functions that I should be using?
Any help would be much appreciated!
PyEval_SetTrace() is exactly the API that you need to use. Not sure why you need some additional way to "pause" the execution; when your callback has been called, the execution is already paused and will not resume until you return from the callback.
Related
Google'd but only getting results about how we can create launch.json configs and start the debugging from line #1.
So I have a [big?] Python project that runs from command-line, and I just created a helper method (def pauseHereAndNotifyUserOnSlack(user=<username>) to pause where needed and wait for the user to press a key to exit out of this [infinite] loop and resume the code.
I am wondering if there's a way to attach my python project while the code is paused, inspect the variables and stuff, and resume execution from there?
(Think C#/C++ has this feature, where they attach using symbols and stuff? Not 100% sure how this works. Maybe I am confusing myself?)
Let me know if you guys need more clarification. TIA
You don't need to debug your code from line 1, set breakpoints in your code and start debugging from there and inspect variables and can also resume execution from there. (if this is what you were talking about)
the play button can be used to resume your execution.
I found myself having to implement the following use case: I need to run a webapp in which users can submit C programs, which need to be run safely on my backend.
I'm trying to get this done using Node. In the past, I had to do something similar but the user-submitted code was JavaScript code, and I got away with using Node vm2 module. Essentially, I would create a VM and call its run method with the user submitted code as a string argument, then collect the output and do whatever I had to.
I'm trying to understand if using the same moule could help me with C code as well. The idea would be to use exec to first call gcc and compile the user code. Afterwards, I would use a VM to run exec again, this time passing the generated executable as a result. Would this be safe?
I don't understand vm2 deeply enough to know whether the safety is only limited to executing JS code or if it can be trusted to also run any arbitrary shell command safely.
In case vm2 isn't appropriate, what would be another way to run an executable in a sandboxed fashion in Node? Feel free to also suggest Python-based solutions, if you know any. Please note that the code will still be executed in a separate container as the main app regardless, but I want to make extra sure users cannot easily just tear it down at their liking.
Thank you in advance.
I am currently experiencing the same challenge as you, trying to execute safely some untrusted code using spawn, so what I can tell you is that vm2 only works for JS/TS code, but can't control what happens to a new process created by spawn, fork or exec.
For now I haven't found any good solution, but I'm thinking of trying to run the process as a user with limited rights.
As you seem to have access to the C source code, I would advise you to search how to run untrusted C programs (in plain C), and see if you can manipulate the C code in order to have a safer environment from this point of view.
I am running some automated tests on an POS application where a large number of sales are entered using a for loop. During the test there are times where it is possible for the application window to lose focus, and when this happened we get a pop up window and this causes the test to stop.
I currently have a lot of checks in the code to look for this window after multiple steps in the loop, but each one I add adds time to the sale and slows the test down. Is there a way in python to constantly check for something like these windows.
To note I am using TestComplete and I have looked into the event handlers and it does not appear I will be able to use them due to how the application was developed.
I recommend you try to use an interrupt schedule. The basic idea is that you trigger a function (in this case your function checking for unexpected windows) whenever some counter reaches a value.
If you don't need to check at very specific and short time intervals it is enough to use something like time.clock(). I you DO need the abovementioned there are libraries for that, specifically the signal module or the more advanced sched, which are both part of the standard library (as far as I know, Documentation of signal, Documentation of sched).
There are also other (external, non-standard) modules that can work, but sched and/or signal should be enough here.
Feel free to ask if any further question should arise.
This SO post might also help: real time interrupts in python
Will it is possible to run a small set of code automatically after a script was run?
I am asking this because for some reasons, if I added this set of code into the main script, though it works, it will displays a list of tab errors (its already there, but it is stating that it cannot find it some sort).
I realized that after running my script, Maya seems to 'load' its own setup of refreshing, along with some plugins done by my company. As such, if I am running the small set of code after my main script execution and the Maya/ plugins 'refresher', it works with no problem. I had like to make the process as automated as possible, all within a script if that is possible...
Thus is it possible to do so? Like a delayed sort of coding method?
FYI, the main script execution time depends on the number of elements in the scene. The more there are, it will takes longer...
Maya has a command Maya.cmds.evalDeferred that is meant for this purpose. It waits till no more Maya processing is pending and then evaluates itself.
You can also use Maya.cmds.scriptJob for the same purpose.
Note: While eval is considered dangerous and insecure in Maya context its really normal. Mainly because everything in Maya is inherently insecure as nearly all GUI items are just eval commands that the user may modify. So the second you let anybody use your Maya shell your security is breached.
I'm programming in python on a pre-existing pylons project (the okfn's ckan), but I'm a lisper by trade and used to that way of doing things.
Please correct me if I make false statements:
In pylons it seems that I should say
$ paster serve --reload
to get a web server that will notice changes.
At that point I can change a function, save the file and then go to my browser to test the change.
If I want to examine variables in a function in the process of making a webpage, then I put raise "hello", and then when I load the page, I get a browser based debugger, in which I can examine the program.
This is all very nice and works swimmingly, and I get the impression that that's how people tend to write pylons code.
Unfortunately the reload takes several seconds, and it keeps breaking my train of thought.
What I'd like to do is to run the web server from emacs, (although a python REPL on the command line would be almost as good), so that I can change a function in the editor and then send the new code to the running process without having to restart it. (with a command line repl I guess I'd have to copy and paste the new thing, but that would also be workable, just slightly less convenient)
Python seems very dynamic, and much like lisp in many ways, so I can't see in principle any reason why that wouldn't work.
So I guess the question is:
Is anyone familiar with the lisp way of doing things, and with Pylons, and can they tell me how to program the lisp way in pylons? Or is it impossible or a bad idea for some reason?
Edit:
I can run the webserver from my python interpreter inside emacs with:
from paste.script.serve import ServeCommand
ServeCommand("serve").run(["development.ini"])
And I can get the code to stop and show me what it's doing by inserting:
import pdb
pdb.set_trace()
so now all I need is a way to get the webserver to run on a different thread, so that control returns to the REPL and I can redefine functions and variables in the running process.
def start_server():
from paste.script.serve import ServeCommand
ServeCommand("serve").run(["development.ini"])
server_thread=threading.Thread(target=start_server)
server_thread.start()
This seems to work, except that if I redefine a function at the REPL the change doesn't get reflected in the webserver. Does anyone know why?
It seems that this way of working is impossible in python for the reason given by TokenMacGuy's comment, i.e. because redefining a class doesn't change the code in an instance of that class.
That seems a terrible shame, since in many other respects python seems very flexible, but it does explain why there's no python-swank!