Chaining exceptions with `raise from` in Python

raise-from.md

>>> try:
...     int("")
... except ValueError:
...     raise RuntimeError

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
RuntimeError

>>> try:
...     int("")
... except ValueError as e:
...     raise RuntimeError from e

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: invalid literal for int() with base 10: ''

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
RuntimeError

>>> try:
...     int("")
... except ValueError:
...     raise RuntimeError from None

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
RuntimeError