Unpacking in Python: Extracting Values from Lists and Tuples

Unpacking is a powerful and versatile concept. This feature allows you to extract values from various iterable data structures, such as tuples, lists, dictionaries, ranges, and even strings. The opposite action is packing. Often, these two concepts are used together simultaneously. Let's break down the topic step by step.

First of all, let's compare unpacking and packing.

Python can both pack and unpack values from iterables in a single assignment. To perform packing, use the * iterable unpacking operator before the variable name.

You will encounter errors if you attempt to unpack a different no of values than variables.

The value on the right side can be a tuple, list, generator, range, dictionary, set, or string. Let's explore each of these with examples.

Note

All values that are written in one line and separated by commas but without parentheses are one tuple. 1, 2, 3 same as (1, 2, 3)

The set is an unordered collection of data.

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# string
a, b, c = "123" #  a = "1", b = "2", c ="3"
# list
a, b, c = [1, 2, 3]   #  a = 1, b = 2, c = 3
# range
a, b, c = range(3) #  a = 0, b = 1, c = 2
# set
a, b, c = {1, 2, 3} #  a = 1, b = 2, c = 3
a, b, c = {3, 2, 1} #  a = 1, b = 2, c = 3

# dict
dict_num = {"one": 1, "two": 2, "three": 3}
a, b, c = dict_num # a = "one", b = "two", c = "three"
a, b, c = dict_num.values() #  a = 1, b = 2, c = 3
a, b, c = dict_num.items() # a = ("one", 1), b = ("two", 2), c = ("three", 3)

# assignment to the list
[a, b, c] = 1, 2, 3  #  a = 1, b = 2, c = 3
[a, b, c] = "123" #  a = "1", b = "2", c ="3"