pythonrc

# Interactive Python REPL startup file. Not a module: it is exec'd by the
# interpreter when PYTHONSTARTUP points here, so it has no .py extension and is
# never imported. It runs only in the REPL, never for scripts and never inside
# pdb, which makes it the right home for comfort tweaks the debugger does not
# get. Standard library only; rich is used when present and skipped otherwise.
#
# PYTHONSTARTUP: https://docs.python.org/3/using/cmdline.html
# Idea: https://treyhunner.com/2025/10/handy-python-repl-modifications/


def _setup_history():
    """Persist REPL history across sessions and cap its length."""
    import atexit
    import os
    import readline

    history = os.path.expanduser("~/.python_history")
    try:
        readline.read_history_file(history)
    except (FileNotFoundError, OSError):
        pass
    readline.set_history_length(10000)

    def _save(path=history):
        try:
            readline.write_history_file(path)
        except OSError:
            pass

    atexit.register(_save)


def _setup_completion():
    """Enable tab completion. PyREPL on 3.13+ already does this; harmless twice."""
    try:
        import readline
        import rlcompleter  # noqa: F401
    except ImportError:
        return
    readline.parse_and_bind("tab: complete")


def _setup_pretty():
    """Pretty-print REPL results: rich when available, else pprint."""
    import sys

    try:
        import rich.pretty
    except ImportError:
        import builtins
        import pprint

        def _displayhook(value):
            if value is None:
                return
            # Mirror the REPL contract: bind the last result to _ and echo it.
            builtins._ = value
            pprint.pprint(value)

        sys.displayhook = _displayhook
    else:
        rich.pretty.install()


def _main():
    # readline is absent on some minimal builds; history and completion just do
    # not load there, which is fine.
    try:
        import readline  # noqa: F401
    except ImportError:
        pass
    else:
        _setup_history()
        _setup_completion()
    _setup_pretty()


_main()

# Keep the namespace clean so dir() in a fresh REPL is not noisy.
del _setup_history, _setup_completion, _setup_pretty, _main