Using Packing and Unpacking for Efficient Code in Python

The most common usage of packing and unpacking can be seen in the following examples.

Values Swapping

Typically, to swap the values of variables, you might use an additional temporary variable:

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a = 2
b = 3

temp = a  # temp = 2, a = 2, b = 3
a = b  # temp = 2, a = 3, b = 3
b = temp  # temp = 2, a = 3, b = 2

Simply put, unpacking enables you to swap values between variables in a more concise manner:

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a, b = 2, 3

a, b = b, a # a = 3, b = 2

Dropping Unneeded Values

If you only need the first values from an iterable object, you can pass the unneeded values to the *_ variable.

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my_list = ['Monica', 25, 'Doctor', 'Brazil']

name, age, *_ = my_list

Note

We use '_' single underscore for ignoring values: It's common to use _ as a throwaway variable to indicate that a specific value in a tuple unpacking is intentionally being ignored.