Simple paging utility for reading long text in the terminal.

pages.py

import curses
import math
import sys
import textwrap


def print_page(screen, pages, index):
    screen.clear()
    screen.addstr(0, 30, f'({index + 1})')

    for i, line in enumerate(pages[index].splitlines()):
        screen.addstr(2 + i, 0, line)

    screen.refresh()


def main(filename):
    def run(stdscr):
        stdscr.clear()
        stdscr.keypad(True)
        curses.curs_set(0)

        max_rows, max_cols = stdscr.getmaxyx()
        top_pad = 2
        height = max_rows - (top_pad * 2)
        width = 60

        container = stdscr.subwin(
            height, width, top_pad, int(max_cols / 2) - int(width / 2)
        )

        with open(filename, 'r') as file:
            text = file.read()
            lines = textwrap.fill(
                text, width, replace_whitespace=False).splitlines()
            n_lines = len(lines)
            lines_per_page = height - 2
            pages = [
                '\n'.join(lines[i:i + lines_per_page])
                for i in range(0, n_lines, lines_per_page)
            ]

        current_page = 0
        print_page(container, pages, current_page)

        while True:
            c = stdscr.getch()
            if c == ord('q'):
                break
            elif c == curses.KEY_RIGHT and current_page < len(pages) - 1:
                current_page += 1
                print_page(container, pages, current_page)
            elif c == curses.KEY_LEFT and current_page > 0:
                current_page -= 1
                print_page(container, pages, current_page)
            elif c == curses.KEY_NPAGE:
                current_page = len(pages) - 1
                print_page(container, pages, current_page)
            elif c == curses.KEY_PPAGE:
                current_page = 0
                print_page(container, pages, current_page)

    return run


if __name__ == '__main__':
    filename = sys.argv[1]
    curses.wrapper(main(filename))