如何保存参数到本地？

from tqsdk import TqApi, TargetPosTask
import json


SYMBOL = "SHFE.au1912"
NUM = 3
api = TqApi()
target_pos = TargetPosTask(api, SYMBOL)
position = api.get_position(SYMBOL)
quote = api.get_quote(SYMBOL)

print("策略开始运行")

try:
    # 读取数据，本策略目标净持仓数
    with open("NUM.json", "r") as r:
        NUM = json.load(r)
# 若读取不成功或第一次运行，则按照之前设定的净持仓目标手数运行
except FileNotFoundError:
    pass
print("当前净持仓数：%d, 目标净持仓数: %d" % (position.pos, NUM))

while True:
    api.wait_update()
    target_pos.set_target_volume(NUM)
    if position.pos == NUM:
        NUM = NUM + 1
        break

print("当前净持仓数：%d" % position.pos)
api.close()
# 保存数据，写入下次净持仓手数
with open("NUM.json", "w") as n:
    json.dump(NUM, n)