How to add a breakpoint in Jupyter notebook?

Question

In Jupyter notebook, if I have

print("hello")
quit()

in the first cell and

print("Good bye")

in the second, when I do "Run all" it prints hello and also Good bye.

In other words, quit() seems to only stop the execution of the cell itself, not the whole script.

Is there some way to add a breakpoint to your code so that it stops executing when it gets to it?

Answer 1

You can use IPython.core.debugger.Pdb to invoke pdb. Insert the following line to set a breakpoint.

from IPython.core.debugger import Pdb; Pdb().set_trace()

See this page for debugger commands.

Also, you can use %debug magic to invoke pdb after an error. Just type %debug to the next cell if an exception occurs. Then pdb runs from its stack frames.

Answer 2

From the JupyterLab docs:

JupyterLab 3.0 now ships with a Debugger front-end by default.

For the debugger to be enabled and visible, a kernel with support for debugging is required.

If you are using Pip, install the Xeus-Python kernel with pip install xeus-python.

Then open a jupyterlab notebook, and choose the new kernel from the toolbar:

You can then debug your code as follows:

Source: https://jupyterlab.readthedocs.io/en/stable/user/debugger.html