Getting the source of an object defined in an iPython session.

[spott]

Usually, if you want to get the source of an object, you can get it via the inspect module:

import inspect
inspect.getsource(MyObject)

However, in a Jupyter notebook / ipython console, this doesn't work:

import inspect

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

inspect.getsource(Foo)

Throws a TypeError: TypeError: <module '__main__'> is a built-in class. This appears to be because __file__ isn't defined in ipython sessions.

Is there a way to inspect an object to get its source in a Jupyter notebook? The only way that comes to mind is something like get_ipython and then walking the history until you find the class definition you want. Is there another way?

This appears to be related to #29, but that was closed, so maybe I'm missing something.

[HackBrettHB]

Is there a solution or workaround to this by now?

[diego898]

Want to refresh this issue

[adivekar-utexas]

Folks, it's been four years...any workaround/potential to fix this?

[s-m-e]

The root problem is inspect.getfile, if I understand it correctly.

Digging around, I found this gem on Stackoverflow - ping @theevann:

import inspect, sys

def new_getfile(object, _old_getfile=inspect.getfile):
    if not inspect.isclass(object):
        return _old_getfile(object)
    
    # Lookup by parent module (as in current inspect)
    if hasattr(object, '__module__'):
        object_ = sys.modules.get(object.__module__)
        if hasattr(object_, '__file__'):
            return object_.__file__
    
    # If parent module is __main__, lookup by methods (NEW)
    for name, member in inspect.getmembers(object):
        if inspect.isfunction(member) and object.__qualname__ + '.' + member.__name__ == member.__qualname__:
            return inspect.getfile(member)
    else:
        raise TypeError('Source for {!r} not found'.format(object))

inspect.getfile = new_getfile

... which allows to retrieve the code of MyClass defined in some cell as follows:

import inspect
from IPython.core.magics.code import extract_symbols

obj = MyClass
cell_code = "".join(inspect.linecache.getlines(new_getfile(obj)))
class_code = extract_symbols(cell_code, obj.__name__)[0][0]
print(class_code)

Bottom line: This proves that it can be done (though it should probably be done better). It would be nice if IPython had similar functionalities for notebooks / sessions as inspect has for regular Python modules.

The lack of an API like this breaks tools like typeguard, among other, see e.g. here.

The CPython project considers this an issue in IPython and refused a change in its standard library - probably correctly, because source code retrieval really depends on (moving) implementation details in IPython.