Jupyter autoreload fails when changing a class

Question

When using jupyter lab/notebook, most of the time, I put those 2 lines in the first cell of my notebook :

%reload_ext autoreload
%autoreload 2

Those usually allow me to modify the scripts I import and to use them without having to reimport them or to relaunch the kernel. Yesterday, I encountered an issue : I modified the script, and executing one cell on the notebook gave me an error. Restarting the kernel and redoing the imports fixed it. I investigated this issue, and tried to create a minimal example.

Let's say you have the following working directory :

+-- nb.ipynb
+-- scripts
|   +-- __init__.py
|   +-- script1.py

The notebook is composed of three cells :

%reload_ext autoreload
%autoreload 2

\

from scripts.script1 import Foo

\

a = Foo(42)

At the beginning of this experiment, script1 contains the following :

class Foo():
    def __init__(self, x):
        self.x = x

Now, we execute the 3 cells of the notebook, and everything works fine. We then go to script1.py and replace its code by :

class Bar():
    def __init__(self, x):
        self.x = x

class Foo(Bar):
    def __init__(self, x):
        super().__init__(x)

We save the file, go back to the notebook, and execute the cell containg a = Foo(42) This gives the following error :

[autoreload of script.script failed: Traceback (most recent call last):
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 245, in check
    superreload(m, reload, self.old_objects)
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 384, in superreload
    update_generic(old_obj, new_obj)
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 323, in update_generic
    update(a, b)
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 288, in update_class
    if update_generic(old_obj, new_obj): continue
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 323, in update_generic
    update(a, b)
  File "/home/user/miniconda3/lib/python3.6/site-packages/IPython/extensions/autoreload.py", line 266, in update_function
    setattr(old, name, getattr(new, name))
ValueError: __init__() requires a code object with 0 free vars, not 1
]

Restarting the kernel or executing the import line again fixes this. Why is autoreload not working in this case?

PS : This was done in python 3.6, and my original issue with this was in python 3.7

It worked for me to interrupt the kernel right after running the cell that uses the changed code, and then to run that cell again. When the cell is run the first time, it seems to stuck, and yields an error when the kernel is interrupted. When run again, it seems to work properly. — Phil Filippak, Sep 03 '19 at 13:23
I'm suffering from that problem too. If it helps, the extension works in the ipython console (instatiated from jupyterlab or the terminal). So I've switched to developing in the terminal for now. Not ideal but it is what it is.. — idoda, Dec 11 '19 at 14:16
I have posted an answer below, pls check if it's helpful. Thanks. — loginmind, Feb 07 '20 at 07:55
I have also added a related answered stackoverflow question in the answers below. I hope it helps. — inpap, Nov 08 '21 at 23:35

loginmind · Answer 1 · 2020-02-07T03:09:32.283

1. About the problem

Why is autoreload not working in this case?

As the error log stated:

setattr(old, name, getattr(new, name))
ValueError: __init__() requires a code object with 0 free vars, not 1

What autoreload does here:

It tries to replace the old __init__() function's (the function before code changed) code object with the the new __init__() function code object. When I check the free vars of __init__() function before and after code changed, I got the results as below:

Code to check:

Foo.__init__.__code__.co_freevars

Results:

Before code changed: () , no free var.

After code changed: ('__class__',) , there is one free var here. That's why the error happen. It cannot replace the old object code with the new one.

2. How to solve the problem

In this case, because autoreload remain the old function object so we cannot do anything but only restart the kernel.

Hope this help.

score 1 · Answer 2 · answered Sep 14 '21 at 20:54

1

The following worked for me:

from importlib import reload  
reload(my_module)

Don't know if this will work in all cases, but much easier than restarting the kernel.

answered Sep 14 '21 at 20:54

skluug

19
3

score 0 · Answer 3 · answered Nov 08 '21 at 23:54

Maybe the accepted answer provided in this stackoverflow question can be of help.

It is also connected to the answer provided by skluug above.

It does not save us the trouble of reimporting Foo but we do not have to restart the kernel each time we want to reload the class.

Jupyter autoreload fails when changing a class

3 Answers3