Dynamically substitute main version in versions.rst from release-cycle.json

conf.py

@@ -1,3 +1,5 @@
+import json
+
 extensions = [
     'notfound.extension',
     'sphinx.ext.extlinks',
@@ -165,8 +167,17 @@
 # sphinx-notfound-page
 notfound_urls_prefix = "/"
 
+# Dynamically expose the Python version associated with the "main" branch.
+# Exactly one entry in ``release-cycle.json`` should have ``"branch": "main"``.
+with open("include/release-cycle.json", encoding="UTF-8") as _f:
+    _cycle = json.load(_f)
+
+_main_version = next(
+    version for version, data in _cycle.items() if data.get("branch") == "main"
+)
+
 # prolog and epilogs
-rst_prolog = """
+rst_prolog = f"""
 .. |draft| replace::
     This is part of a **Draft** of the Python Contributor's Guide.
     Text in square brackets are notes about content to fill in.
@@ -183,6 +194,8 @@
 
 .. _Refactoring the DevGuide: https://discuss.python.org/t/refactoring-the-devguide-into-a-contribution-guide/63409
 
+.. |main_version| replace:: {_main_version}
+
 """
 
 # sphinx.ext.extlinks

versions.rst

@@ -5,7 +5,7 @@
 Status of Python versions
 =========================
 
-The ``main`` branch is currently the future Python 3.14, and is the only
+The ``main`` branch is currently the future Python |main_version|, and is the only
 branch that accepts new features.  The latest release for each Python
 version can be found on the `download page <https://www.python.org/downloads/>`_.