What Does the Slash \'/\' Mean in Python\'s `help()` Function Signatures?

Understanding the Slash (/) in help() Method Signature Lists

Python's help() function provides detailed information about classes and functions, including their signatures. When examining the output of help(range) in Python 3.4, users may encounter a slash (/) character before the closing parenthesis in the method signatures.

What Does the Slash Signify?

The slash indicates the demarcation between positional-only parameters and other parameters that can be passed using keyword arguments. Positional-only parameters, introduced in Python 3.8, must be passed in their specified position and cannot be passed as keyword arguments.

In the Case of range()

The range() function has two methods with positional-only parameters: __contains__() and __eq__(). These parameters are key and value, respectively. This means that these parameters can only be passed by position, such as range(5).__contains__(3) and range(5).__eq__(10). Using keyword arguments, such as range(5).__contains__(key=3) and range(5).__eq__(value=10), is not allowed.

Consequences of Positional-Only Parameters

Positional-only parameters have several implications:

• They make pure-Python implementations of C-only modules more consistent and easier to maintain.
• They can lead to cleaner and clearer APIs by providing a clear distinction between positional and keyword arguments.
• They can result in faster Python code because they require less processing.

Additional Resources

For more information on positional-only parameters, refer to the following resources:

• [Argument Clinic Documentation](https://docs.python.org/3/library/argparse.html#extending-argument-parser)
• [Python FAQ](https://docs.python.org/3/faq/programming.html#why-did-the-help-for-a-function-signature-change)
• [PEP 570 - Python Positional-Only Parameters](https://peps.python.org/pep-0570/)

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