Double question mark thing: If you type two question marks after a Python object in ipython, it shows the annotations and source code related to that object: 
In [1]: from asdf import Asdf

In [2]: Asdf??
Init signature: Asdf(qwer: int, zxcv: str) -> None
Source:
class Asdf:
    """This thing does stuff.

    It can foo and bar.
    """

    qwer: int
    zxcv: str
File:           ~/asdf.py
Type:           type
Subclasses:
A W E S O M E S A U C E

I have probably wanted this every day without knowing it!

@python group # #