The Python community has a well-established way of dealing with changes. While speculative Python language ideas are mostly discussed on specific mailing lists (<[email protected]>), nothing major ever gets changed without the existence of a new document called a PEP. A PEP is a Python Enhancement Proposal. It is a paper written that proposes a change on Python, and is a starting point for the community to discuss it. The whole purpose, format, and workflow around these documents is also standardized in the form of a Python Enhancement Proposal—precisely, PEP 1 document (http://www.python.org/dev/peps/pep-0001).

PEP documents are very important for Python and depending on the topic, they serve different purposes:

A list of all the proposed PEPs is available as in a document—PEP 0 (https://www.python.org/dev/peps/). Since they are easily accessible in one place and the actual URL is also very easy to guess, they are usually referred to by the number in the book.

Those who are wondering what the direction is in which the Python language is heading but do not have time to track a discussion on Python mailing lists, the PEP 0 document can be a great source of information. It shows which documents have already been accepted but are not yet implemented and also which are still under consideration.

PEPs also serve additional purposes. Very often, people ask questions like:

In most such cases, the extensive answer is available in specific PEP documents where such a feature has already been mentioned. There are a lot of PEP documents describing Python language features that were proposed but not accepted. These documents are left as a historical reference.