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Python breakpoint() is a new built-in function introduced in Python 3.7. Python code debugging has always been a painful process because of the tight coupling between the actual code and the debugging module code. For example, if you are using pdb debugger, then you will have to call
pdb.set_trace() in your program code. If you want to use any other debugger, let’s say
web-pdb then you will have to remove all the code related to PDB and add
web_pdb.set_trace() method. This causes a huge overhead in using python debugger and makes the python code hard to debug and maintain. That’s why Python 3.7 has introduced
breakpoint() method that allows us to write loosely coupled debugging code.
Python breakpoint() function calls
sys.breakpointhook() function. By default, sys.breakpointhook() calls
pdb.set_trace() function. So at the very least, using breakpoint() provide convenience in using a debugger because we don’t have to explicitly import
pdb module. Let’s look at a simple example of breakpoint() function usage. We have a python script
python_breakpoint_examples.py with the following code.
x = 10 y = 'Hi' z = 'Hello' print(y) breakpoint() print(z)
When we execute this script, the PDB debugger console opens up.
$python3.7 python_breakpoint_examples.py Hi > /Users/pankaj/Documents/PycharmProjects/BasicPython/basic_examples/python_breakpoint_examples.py(8)() -> print(z) (Pdb) c Hello $
Python sys.breakpointhook() function uses environment variable PYTHONBREAKPOINT to configure the debugger. If unset, the default PDB debugger is used. If it’s set to “0” then the function returns immediately and no code debugging is performed. It’s very helpful when we want to run our code without debugging.
$PYTHONBREAKPOINT=0 python3.7 python_breakpoint_examples.py Hi Hello $
We can use PYTHONBREAKPOINT environment variable to provide the debugger method to be called by breakpoint() function. This is very helpful because we can change the debugger module easily without making any code change. Let’s say we want to use
web-pdb debugger. We can easily hook it into our program using
PYTHONBREAKPOINT=web_pdb.set_trace. First of all, make sure that web-pdb is installed. You can install it using
pip3.7 install web-pdb command.
According to web-pdb documentation, it’s compatible with the new breakpoint() function added in Python 3.7.
$PYTHONBREAKPOINT=web_pdb.set_trace python3.7 python_breakpoint_examples.py Hi 2018-08-10 12:49:54,339: root - web_console:110 - CRITICAL - Web-PDB: starting web-server on pankaj:5555...
Open the web-server URL provided in the console log and you will see the debugger window like the below image. We can issue PDB commands using this UI, you can send command “c” to continue and complete our program.
Python breakpoint() function is a very helpful addition to the python debugging feature. It’s recommended to use this for debugging so that you can easily hook other third-party debuggers on the fly. It also provides an easy option to disable the debugger and runs the program normally.
You can check out more Python examples from our GitHub Repository.
Reference: Official Documentation
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