An IPython notebook satrtup script to enable the use of mypy within jupyter notebooks

MypyTypecheck.py

#! /usr/bin python3
# -*- coding:utf-8 -*-
"""
Add mypy type-checking ability to jupyter/ipython.

Save this script to your ipython profile's startup directory.

IPython's directories can be found via `ipython locate [profile]` to find the current ipython directory and ipython profile directory, respectively.

For example, this file could exist on a path like this on mac:

/Users/yourusername/.ipython/profile_default/startup/typecheck.py

where /Users/yourusername/.ipython/profile_default/ is the ipython directory for the default profile.

and the jupyter/ipython shell will do typecheck automatically.
"""

import re
from IPython import get_ipython
mypy_cells = ''
mypy_shell = get_ipython()
mypy_tmp_func = mypy_shell.run_cell
mypy_typecheck=True
def mypy_tmp(cell,*args,**kwargs):
    if mypy_typecheck:
        from mypy import api

        global mypy_cells
        
        mypy_cells_length = len(mypy_cells.split('\n'))-1
        mypy_cells+=(cell+'\n')
        mypy_result = api.run(['-c', mypy_cells])
        if mypy_result[0]:
            for line in mypy_result[0].strip().split('\n'):
                l,n,r = re.compile('(<[a-z]+>:)(\d+)(.*?)$').findall(line)[0]
                if int(n)>mypy_cells_length:
                    n = str(int(n)-mypy_cells_length)
                    print("".join([l,n,r]))
        if mypy_result[1]:
            print(mypy_result[1])
    return mypy_tmp_func(cell,*args,**kwargs)
mypy_shell.run_cell = mypy_tmp

... works for a single run-through but not optimal for interactive use: mypy_cells keeps growing. Should be tracking cell modifications and deletions. Another question is - which cells should be re-evaluated by mypy to create the context for the current cell? All cells in the notebook? Perhaps not; maybe all cells with a magic marker.

The standard operating mechanism for a jupyter notebook is that the context for evaluating the current cell is precisely evaluating all previous cells in the order in which they were evaluated. Clearly any type-checking must use the same semantics.

I'm working on a facility based on this, to have some interactive use. It is internal for now, but I'll share it when I can.

Thanks for the initial gist btw!

We've made it into an iPython extension, which can be found here: https://pypi.org/project/nb-mypy/