PEP 648: Add entry points as rejected alternative (#1784)

pep-0648.rst

@@ -94,8 +94,10 @@ Rationale
 
 This PEP proposes supporting extensible customization of the interpreter at
 startup by allowing users to install scripts into a folder named
-``__sitecustomize__`` located in a site path. Those scripts will be executed
-at startup time.
+``__sitecustomize__`` located in any site path. Those scripts will be executed
+at startup time. The implementation will take advantage of the fact that all
+site paths are already being walked to look for ``pth`` files to include also a
+check for ``__sitecustomize__`` folders and execute all scripts within them.
 
 The ``site`` module will expose an option on its main function that allows
 listing all scripts that will be executed, which will allow users to quickly
@@ -271,6 +273,22 @@ Support for shutdown custom scripts
 could also add code at shutdown, but extra support for that is not needed, as
 Python users can already do that via ``atexit``.
 
+Using entry_points
+------------------
+
+We considered extending the use of entry points to allow specifying scripts
+that should be executed at startup but we discarded that solution due to two
+main reasons. The first one being impact on startup time. This approach will
+require scanning all packages distribution information to just execute a
+handful of files.  This has an impact on performance even if the user is not
+using the feature and such impact growths linearly with the number of packages
+installed in the environment.  The second reason was that the proposed
+implementation in this PEP offers a single solution for startup customization
+for packages and system administrators.  Additionally, if the main objective of
+entry points is to make it easy for libraries to install scripts at startup,
+that can still be added and make the build backends just install the files
+within the ``__sitecustomize__`` folder.
+
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