python_startup.py

import readline
import rlcompleter
from os.path import expanduser


class irlcompleter(rlcompleter.Completer):
    def complete(self, text, state):
        spaces = ' ' * 4
        if not text:
            # Replace \t to 4 or 8 spaces if you prefer indent via spaces.
            return [spaces, None][state]
        else:
            return super().complete(text, state)


# This line could bind to another key instead tab.
readline.parse_and_bind("tab: complete")
readline.set_completer(irlcompleter().complete)

# I setup $PYTHON_STARTUP to `~/.python/startup.py`.
# To be consistent, `~/.python_history` is moved to the following location.
readline.read_history_file(expanduser("~/.python/history"))