How to detect that Python code is being executed through the debugger?
Question:
Is there a simple way to detect, within Python code, that this code is being executed through the Python debugger?
I have a small Python application that uses Java code (thanks to JPype). When I’m debugging the Python part, I’d like the embedded JVM to be passed debug options too.
Answers:
From taking a quick look at the pdb docs and source code, it doesn’t look like there is a built in way to do this. I suggest that you set an environment variable that indicates debugging is in progress and have your application respond to that.
$ USING_PDB=1 pdb yourprog.py
Then in yourprog.py:
import os
if os.environ.get('USING_PDB'):
# debugging actions
pass
Python debuggers (as well as profilers and coverage tools) use the sys.settrace function (in the sys module) to register a callback that gets called when interesting events happen.
If you’re using Python 2.6, you can call sys.gettrace() to get the current trace callback function. If it’s not None then you can assume you should be passing debug parameters to the JVM.
It’s not clear how you could do this pre 2.6.
You can try to peek into your stacktrace.
https://docs.python.org/library/inspect.html#the-interpreter-stack
when you try this in a debugger session:
import inspect
inspect.getouterframes(inspect.currentframe()
you will get a list of framerecords and can peek for any frames that refer to the pdb file.
A solution working with Python 2.4 (it should work with any version superior to 2.1) and Pydev:
import inspect
def isdebugging():
for frame in inspect.stack():
if frame[1].endswith("pydevd.py"):
return True
return False
The same should work with pdb by simply replacing pydevd.py with pdb.py. As do3cc suggested, it tries to find the debugger within the stack of the caller.
Useful links:
If you’re using Pydev, you can detect it in such way:
import sys
if 'pydevd' in sys.modules:
print "Debugger"
else:
print "commandline"
Another way to do it hinges on how your python interpreter is started. It requires you start Python using -O for production and with no -O for debugging. So it does require an external discipline that might be hard to maintain .. but then again it might fit your processes perfectly.
From the python docs (see “Built-in Constants” here or here):
__debug__
This constant is true if Python was not started with an -O option.
Usage would be something like:
if __debug__:
print 'Python started without optimization'
I found a cleaner way to do it,
Just add the following line in your manage.py
#!/usr/bin/env python
import os
import sys
if __debug__:
sys.path.append('/path/to/views.py')
if __name__ == "__main__":
....
Then it would automatically add it when you are debugging.
Other alternative if you’re using Pydev that also works in a multithreading is:
try:
import pydevd
DEBUGGING = True
except ImportError:
DEBUGGING = False
Since the original question doesn’t specifically call out Python2 – This is to confirm @babbageclunk’s suggested usage of sys also works in python3:
from sys import gettrace as sys_gettrace
DEBUG = sys_gettrace() is not None
print("debugger? %s" % DEBUG)
In my perllib, I use this check:
if 'pdb' in sys.modules:
# We are being debugged
It assumes the user doesn’t otherwise import pdb
Is there a simple way to detect, within Python code, that this code is being executed through the Python debugger?
I have a small Python application that uses Java code (thanks to JPype). When I’m debugging the Python part, I’d like the embedded JVM to be passed debug options too.
From taking a quick look at the pdb docs and source code, it doesn’t look like there is a built in way to do this. I suggest that you set an environment variable that indicates debugging is in progress and have your application respond to that.
$ USING_PDB=1 pdb yourprog.py
Then in yourprog.py:
import os
if os.environ.get('USING_PDB'):
# debugging actions
pass
Python debuggers (as well as profilers and coverage tools) use the sys.settrace function (in the sys module) to register a callback that gets called when interesting events happen.
If you’re using Python 2.6, you can call sys.gettrace() to get the current trace callback function. If it’s not None then you can assume you should be passing debug parameters to the JVM.
It’s not clear how you could do this pre 2.6.
You can try to peek into your stacktrace.
https://docs.python.org/library/inspect.html#the-interpreter-stack
when you try this in a debugger session:
import inspect
inspect.getouterframes(inspect.currentframe()
you will get a list of framerecords and can peek for any frames that refer to the pdb file.
A solution working with Python 2.4 (it should work with any version superior to 2.1) and Pydev:
import inspect
def isdebugging():
for frame in inspect.stack():
if frame[1].endswith("pydevd.py"):
return True
return False
The same should work with pdb by simply replacing pydevd.py with pdb.py. As do3cc suggested, it tries to find the debugger within the stack of the caller.
Useful links:
If you’re using Pydev, you can detect it in such way:
import sys
if 'pydevd' in sys.modules:
print "Debugger"
else:
print "commandline"
Another way to do it hinges on how your python interpreter is started. It requires you start Python using -O for production and with no -O for debugging. So it does require an external discipline that might be hard to maintain .. but then again it might fit your processes perfectly.
From the python docs (see “Built-in Constants” here or here):
__debug__
This constant is true if Python was not started with an -O option.
Usage would be something like:
if __debug__:
print 'Python started without optimization'
I found a cleaner way to do it,
Just add the following line in your manage.py
#!/usr/bin/env python
import os
import sys
if __debug__:
sys.path.append('/path/to/views.py')
if __name__ == "__main__":
....
Then it would automatically add it when you are debugging.
Other alternative if you’re using Pydev that also works in a multithreading is:
try:
import pydevd
DEBUGGING = True
except ImportError:
DEBUGGING = False
Since the original question doesn’t specifically call out Python2 – This is to confirm @babbageclunk’s suggested usage of sys also works in python3:
from sys import gettrace as sys_gettrace
DEBUG = sys_gettrace() is not None
print("debugger? %s" % DEBUG)
In my perllib, I use this check:
if 'pdb' in sys.modules:
# We are being debugged
It assumes the user doesn’t otherwise import pdb