What Does a Slash Mean in Python\'s `help()` Output?

When a Slash Appears in help() Output: Positional-Only Parameters

When using Python's help() function to explore the signature of a method or function, you may encounter a slash (/) in the output before the closing parenthesis. This symbol indicates the end of the function's positional-only parameters.

What are Positional-Only Parameters?

Positional-only parameters are parameters that cannot be passed as keyword arguments. They must be specified in their correct positional order when calling the function or method.

Before Python 3.3, positional-only parameters were not officially supported in the Python language. However, they could be defined in C extensions using the Argument Clinic tool.

In Python 3.8, positional-only parameters were officially introduced as part of the language specification. They are now supported in both C extensions and pure Python code.

How to Use Positional-Only Parameters

To define a positional-only parameter, simply place a slash (/) on a line by itself after the last positional parameter in the function signature. For example:

def my_function(a, b, /):
    pass

In this example, a and b are positional parameters, while the slash indicates that any further parameters must be positional-only.

Benefits of Positional-Only Parameters

Using positional-only parameters can offer several benefits:

• Cleaner and Clearer APIs: By restricting the use of keyword arguments for certain parameters, you can make function signatures more concise and readable.
• Consistent Implementations: Positional-only parameters allow for more consistent implementations of Python modules that wrap C code.
• Faster Code: Positional-only parameters require less processing, which can result in faster execution times for Python code.

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