[998] Python unpacking operators (* and **)

ref: Python unpacking operators (* and **) (RECOMMENDED)

ref: Python Functions

ref: Python Unpack Dictionary: A Comprehensive Guide

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Here are some crucial things for take-away of the unpacking operators:

• A single asterisk * unpacks items from lists, tuples, sets, and strings;
• A double asterisk ** unpacks dictionaries;
• Using a single asterisk on a dictionary will unpack only dictionary keys;
• You can pass all iterable items to a function with the help of unpacking operators;
• You can merge and update iterables using the starred expressions.

Some examples:

The double asterisk can merge several dictionaries:

dict_1 = {'a': 1, 'b': 2, 'c': 3}
dict_2 = {'one': 'two', 'three': 'four'}
 
dict_3 = {**dict_1, **dict_2}
# {'a': 1, 'b': 2, 'c': 3, 'one': 'two', 'three': 'four'}

You can merge not only multiple dictionaries but also add extra key-value pairs to the existing ones. For instance:

my_dict = {'apple': 1, 'banana': 2, 'pear': 3}
my_dict_updated = {**my_dict, 'strawberry': 4}
print(my_dict_updated)
# {'apple': 1, 'banana': 2, 'pear': 3, 'strawberry': 4}

Or even create a copy of a dictionary and update its values at the same time:

my_dict = {'apple': 1, 'banana': 2, 'pear': 3}
my_dict_copy = {**my_dict, 'apple': 100}
print(my_dict_copy)
# {'apple': 100, 'banana': 2, 'pear': 3}