What is the right way to debug in iPython notebook?

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As I know, %debug magic can do debug within one cell.

However, I have function calls across multiple cells.

For example,

In[1]: def fun1(a)
           def fun2(b)
               # I want to set a breakpoint for the following line #
               return do_some_thing_about(b)

       return fun2(a)

In[2]: import multiprocessing as mp
       results=pool.map(fun1, 1.0)

What I tried:

  1. I tried to set %debug in the first line of cell-1. But it enter into debug mode immediately, even before executing cell-2.

  2. I tried to add %debug in the line right before the code return do_some_thing_about(b). But then the code runs forever, never stops.

What is the right way to set a break point within the ipython notebook?

Use ipdb

Install it via

pip install ipdb


In[1]: def fun1(a):
   def fun2(a):
       import ipdb; ipdb.set_trace() # debugging starts here
       return do_some_thing_about(b)
   return fun2(a)
In[2]: fun1(1)

For executing line by line use n and for step into a function use s and to exit from debugging prompt use c.

For complete list of available commands: https://appletree.or.kr/quick_reference_cards/Python/Python%20Debugger%20Cheatsheet.pdf

Jupyter Tips and Tricks - Christoph Rieke, Use ipdb. Install it via pip install ipdb. Usage: In[1]: def fun1(a): def fun2(a): import ipdb; ipdb.set_trace() # debugging starts here return  Edit: the functions above are deprecated since IPython 5.1. This is the new approach: from IPython.core.debugger import set_trace. Add set_trace() where you need a breakpoint. Type help for ipdb commands when the input field appears.

You can use ipdb inside jupyter with:

from IPython.core.debugger import Tracer; Tracer()()

Edit: the functions above are deprecated since IPython 5.1. This is the new approach:

from IPython.core.debugger import set_trace

Add set_trace() where you need a breakpoint. Type help for ipdb commands when the input field appears.

What is the right way to debug in iPython notebook?, Most Python IDEs have good debuggers built into them. But what if you want to debug the code in your Jupyter Notebook? One way to figure out what is going on is by adding a breakpoint using pdb's set_trace() function:. Here’s how to debug your code when using a Jupyter/iPython notebook. Use Tracer()(). Here’s an example using a simple function (based on this lucid explanation). When the debugger reaches the Tracer()() line, a small line to type in commands will appear under your cell. Simply type in the variable names to check the values or run other commands.

Your return function is in line of def function(main function), you must give one tab to it. And Use


instead of


to debug the whole cell not only line. Hope, maybe this will help you.

Jupyter Notebook Debugging, While searching for ways to debug code in a Jupyter notebook, I found a lot of outdated posts. So I decided to quickly write up my findings. IPython also has a debugger called ipdb. However it does not work with Jupyter Notebook directly. You would need to connect to the kernel using something like Jupyter console and run it from there to use it. If you would like to go that route, you can read more about using Jupyter console here.

You can always add this in any cell:

import pdb; pdb.set_trace()

and the debugger will stop on that line. For example:

In[1]: def fun1(a):
           def fun2(a):
               import pdb; pdb.set_trace() # debugging starts here
           return fun2(a)

In[2]: fun1(1)

Debugging Jupyter notebooks, Don't get me (or Tenderlove) wrong - the debugger that comes with a good IDE is one of the most powerful tools that a programmer can have! The easiest way to debug a Jupyter notebook is to use the %debug magic command. Whenever you encounter an error or exception, just open a new notebook cell, type %debug and run the cell. This will

Just type import pdb in jupyter notebook, and then use this cheatsheet to debug. It's very convenient.

c --> continue, s --> step, b 12 --> set break point at line 12 and so on.

Some useful links: Python Official Document on pdb, Python pdb debugger examples for better understanding how to use the debugger commands.

Some useful screenshots:

5 Ways of Debugging with IPython, Good to know. Reply. Questions/comments? If you just want to say thanks, consider sharing this article or following me on Twitter  What is the right way to debug in iPython notebook? 75. IPython Notebook cell multiple outputs. Hot Network Questions

How to debug a Jupyter/iPython notebook, Most of the time when a Python script fails, it will raise an Exception. There are many ways to launch and use both these debuggers; we won't cover them fully  Using the Tracer class was actually the first thing I found when looking for information regarding debugging Jupyter notebooks. def add_to_life_universe_everything (x): answer = 42 from IPython.core.debugger import Tracer; Tracer ()() answer += x return answer add_to_life_universe_everything (12) This brings up the debugging shell, but prompts

Errors and Debugging, A normal way to do that is to add the print statement in your code which helps us track down the source of many issues. import random def  The IPython Notebook is now known as the Jupyter Notebook. It is an interactive computational environment, in which you can combine code execution, rich text, mathematics, plots and rich media. For more details on the Jupyter Notebook, please see the Jupyter website.

Debugging Jupyter Notebooks Will Boost Your Productivity, Jupyter users like to experiment in the notebook, and to use the notebook Xeus​-python was an appropriate choice for this first implementation of the The following diagram shows how the debug messages flow between  Very importantly, this means that the %debug magic does not work in the notebook! We intend to correct this limitation, but in the meantime, there is a way to debug problems in the notebook: you can attach a Qt console to your existing notebook kernel, and run %debug from the Qt console.

  • ipdb does't give me the debug prompt in the other cell with the sample code mentioned in the question. Now the code keeps running forever.
  • @Rex For me it works. Where did you put ipdb? Put import ipdb; ipdb.set_trace(); before the line return do_some_thing_about(b). Then, call fun1(a) from second cell, it should work. For exiting the debugging promt use 'c'
  • @Rex Updated the answer for more clarity.
  • This works in iPython console but not in iPython notebook (which is what the question asked). When I type import ipdb; ipdb.set_trace() within a notebook cell it says MultipleInstanceError: Multiple incompatible subclass instances of TerminalIPythonApp are being created.
  • new to jupyter...it seems that it is more suitable for presentation and sharing code snippets...can we have functionality that IDEs (like eclipse, rstudio) provide like actual debugging, step through, breakpoints, adding watch to the expression and variables etc. At first, it seems that it is not the case, just want to be sure.....
  • Tracer was depreciated. Now it works this way: from IPython.core.debugger import set_trace and set_trace() evokes a breakpoint. Source: davidhamann.de/2017/04/22/debugging-jupyter-notebooks
  • Should that be ipdb?
  • @Rex Not necessarily. ipdb is a refactor of the Python Debugger that is more closely integrated with IPython. pdb is built in.
  • ipdb can also be used outside the ipython shell and comes with some conveniences like tab completion.
  • Good answer. However, I think (I am new to Jupyter notebook) one should add %debug to set a breakpoint.