python: enforce XDG for python_history

dot_config/python/pythonrc

@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# This entire thing is unnecessary post v3.13.0a3
+# https://github.com/python/cpython/issues/73965
+
+
+def is_vanilla() -> bool:
+    """:return: whether running "vanilla" Python"""
+    import sys
+
+    return not hasattr(__builtins__, "__IPYTHON__") and "bpython" not in sys.argv[0]
+
+
+def setup_history():
+    """read and write history from state file"""
+    import os
+    import atexit
+    import readline
+    from pathlib import Path
+
+    # https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables
+    if state_home := os.environ.get("XDG_STATE_HOME"):
+        state_home = Path(state_home)
+    else:
+        state_home = Path.home() / ".local" / "state"
+        if not state_home.is_dir():
+            print("Error: XDG_SATE_HOME does not exist at", state_home)
+
+            history: Path = state_home / "python_history"
+
+            # https://github.com/python/cpython/issues/105694
+            if not history.is_file():
+                with open(history, "w") as f:
+                    f.write(
+                        "_HiStOrY_V2_"
+                        + "\
+\
+                "
+                    )  # breaks on macos + python3 without this.
+
+    readline.read_history_file(history)
+    atexit.register(readline.write_history_file, history)
+
+
+if is_vanilla():
+    setup_history()