do_config.py

# script to get the configuration file based on a jinja2 template. 
# Usage python do_config.py template_file.j2
# it will generate a cfg.txt file with the output shown
# Example j2 template file:
#
# {{ vlan_tag }}
# {{ vlan_description }}
# {{ int_out_to_peer }}
# {{ vpn_instance }}
# {{ ip_vlan_svi }}
# {{ mask_vlan_svi }}
# {{ ip_vlan_svi_peer }}
# 
# sys
# #
# vlan {{ vlan_tag }}
#  name {{ vlan_description }}
#  description {{ vlan_description }}
# #
# interface {{ int_out_to_peer }}
#  port trunk allow-pass vlan {{ vlan_tag }}
# #
# int vlan {{ vlan_tag }}
#  description {{ vlan_description }}
#  ip binding vpn-instance {{ vpn_instance }}
#  ip address {{ ip_vlan_svi }} {{ mask_vlan_svi }}
#  undo icmp host-unreachable send
#  undo icmp redirect send
# #
# bgp 65500
#  ipv4-family vpn-instance {{ vpn_instance }}
#   peer {{ ip_vlan_svi_peer }} as-number 65000
#   peer {{ ip_vlan_svi_peer }} fake-as 65556
# #
# quit
# save all


from jinja2 import Template, Environment, meta
import os
from typing import Set
import argparse



def get_variables(file: str) -> Set:
    path =  os.getcwd()
    filename = f'{path}/{file}'
    with open(filename) as f:
        template = f.read()
    env = Environment()
    ast = env.parse(template)
    r = meta.find_undeclared_variables(ast)
    return r


def load_template(file: str, d) -> str:
    path =  os.getcwd()
    filename = f'{path}/{file}'

    with open(filename) as f:
        template = Template(f.read())
    r = template.render(d)
    return r


def main() -> None:
    parser = argparse.ArgumentParser(description='Process template...')
    parser.add_argument('jinja2_template')
    args = parser.parse_args()
    var_d = get_variables(args.jinja2_template)
    r = {}
    for n in var_d:
        r[n] = input(f'{n}: ')

    cfg = load_template(args.jinja2_template, r)
    with open('config.txt', 'w') as f:
        f.write(cfg)
    print(cfg)

if __name__ == '__main__':
    main()