7 Uses of Underscore in Python

Must-know for Python programmers.

Underscore (_) has so many usages in Python.

Today, I want to walk you through 7 of them, which I find pretty useful from time to time.

Let’s begin!

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#1) Retrieve the last computed value

One of the most elegant utilities of underscore is to retrieve the last computed value, as demonstrated below:

This works both in a script (.py) and an interactive environment like Jupyter Notebook.

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#2) Placeholder for loop variable

Instead of explicitly declaring a loop variable, one can also run loops as follows:

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#3) Digit separator

When declaring large numbers, it can be difficult to interpret them. Underscore simplifies this:

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#4-7) Declaring names

We can also use underscore while naming objects.

• A single leading underscore is used to declare variables for internal use. Thus, they cannot be imported during wild imports (from file import *)

• A single trailing underscore is used to avoid conflict with reserved keywords, as depicted below:

• Double leading underscores are used to invoke name mangling. This way, one can prevent direct access to private variables outside a class:

We covered this in detail in this issue: Python Does Not Fully Deliver OOP Encapsulation Functionalities.

• Finally, double leading and trailing underscores, as you may already know, are used to define magic methods:

This is a guide on the 20 most common magic methods in Python:

Read this issue for more details: A Consolidated List of 20 Most Common Magic Methods.

Done!

These were the 7 elegant ways to use the underscore keyword in Python.

👉 Over to you: What other usages have I missed?

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