What Are the Multiple Uses of the Underscore Variable (_) in Python?

The Many Roles of the Underscore Variable in Python: From Syntax to Throwaway

The humble underscore variable (_) plays a multifaceted role in Python, serving various purposes ranging from syntax to code readability.

For instance, in the given code snippet, the use of _ after the for loop is a convention indicating that the iteration variable is unimportant or unused. This is especially common when iterating through a collection's elements and only interested in its size or performing some operations without explicitly using the individual values.

Beyond this convention, _ has three primary conventional uses in Python:

1. Holding Last Expression Result: In interactive interpreter sessions, _ holds the result of the most recently evaluated expression.
2. Translation Lookup: _ serves as a placeholder for i18n translation lookups, facilitating the retrieval of localized text.

3. "Throwaway" Variable: _ is frequently employed as a "throwaway" variable:

   • Ignoring Result Values: To suppress unwanted results in function calls, _ can be used as a named placeholder to bind the unused values.
   • Irrelevant Function Arguments: In function definitions that require specific signatures but don't utilize all parameters, _ can indicate unused arguments.

Linters commonly recognize this convention, raising warnings if unused variables are not explicitly declared as _. This helps identify potential bugs and enforce code quality standards.

In Python 3.10, the pattern matching feature has elevated the use of _ in match statements. Here, _ serves as a wildcard pattern, allowing for more concise and expressive matching scenarios.

Remember that _ remains a valid variable name, and its usage can impact memory management. To explicitly release references and prevent unused variables from keeping objects alive, the del name statement can be employed.

The above is the detailed content of What Are the Multiple Uses of the Underscore Variable (_) in Python?. For more information, please follow other related articles on the PHP Chinese website!