What is the right way to debug in iPython notebook?

Question

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
       pool=mp.Pool(processes=2)
       results=pool.map(fun1, 1.0)
       pool.close()
       pool.join

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?

Answer 1

You can use ipdb inside jupyter with:

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

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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.