When I use the library to split window, I use win.cmd('split-window', '-h') which let me spend a lot of time.

At last, I suggest to use bash script instead of this library.

#!/usr/bin/env python3
# coding=utf-8
# author: thinkycx
# date: 2018-01-11
# Usage:
#    run several commands in tmux panel, every window have 4 panes
#    $ pip3 install libtmux
#    $ python tmux.py


import libtmux
import math
import os
import logging

def create_session(session_name, commands):
    '''
        create session with 2*2 panes and run commands
    :param session_name: tmux session name
    :param commands: bash commands
    :return:
    '''
    logging.info(commands)
    # pane_NUM = 3
    # WINDOW_NUM = int(math.ceil(len(commands)/4.0))  # in python3, we can use 4 also

    server = libtmux.Server()
    session = server.new_session(session_name)

    # create windows
    windows = []
    panes = []

    for i in range(len(commands)):
        # create window to store 4 panes
        if i % 4 == 0:
            win = session.new_window(attach=False, window_name="win"+str(int(i/4)))
            windows.append(win)

            # tmux_args = ('-h',)
            win.cmd('split-window', '-h')
            win.cmd('split-window', '-f')
            win.cmd('split-window', '-h')

            panes.extend(win.list_panes())

        panes[i].send_keys(commands[i])

    logging.info(panes)
    logging.info(windows)


if __name__ == '__main__':
    commands = []
    for i in range(10):
        commands.append("echo " + str(i))

    os.system("tmux kill-session -t session")
    create_session("session", commands)