python-nuggets

Unpacking Generalizations

NOTE: Python 3.5+ only!

* iterable unpacking operator

** dictionary unpacking operator

Ordering of argument types in a function call: positional, keyword, * or **.

Unpacking is allowed inside tuple, list, set, and dictionary:

>>> *range(4), 4
(0, 1, 2, 3, 4)
>>> [*range(4), 4]
[0, 1, 2, 3, 4]
>>> {*range(4), 4}
{0, 1, 2, 3, 4}
>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}

In dictionaries, later values will always override earlier ones:

>>> {'x': 1, **{'x': 2}}
{'x': 2}

Useful for merging multiple dictionaries.

>>> first = {'a': 5, 'b': 10}
>>> second = {'b': 6, 'c': 15}
>>> {**first, **second}
{'a': 5, 'b': 6, 'c': 15}

References: https://www.python.org/dev/peps/pep-0448/