用python写一个火车票购买系统，有成人与儿童票，可以查询余票和退票等

好的，下面是一个简单的实现示例：

import random

# 火车票信息
tickets = [
    {"train_no": "G1234", "from_station": "北京", "to_station": "上海", "start_time": "08:00", "end_time": "13:00", "price": 500, "adult_num": 100, "child_num": 50},
    {"train_no": "G2345", "from_station": "上海", "to_station": "北京", "start_time": "14:00", "end_time": "19:00", "price": 500, "adult_num": 80, "child_num": 30},
    {"train_no": "G3456", "from_station": "北京", "to_station": "广州", "start_time": "09:00", "end_time": "18:00", "price": 800, "adult_num": 120, "child_num": 60},
    {"train_no": "G4567", "from_station": "广州", "to_station": "北京", "start_time": "10:00", "end_time": "19:00", "price": 800, "adult_num": 100, "child_num": 40},
]

# 用户信息
users = [
    {"name": "张三", "id_card": "110101199001010001", "order_history": []},
    {"name": "李四", "id_card": "110101199101010001", "order_history": []},
]

# 订单号
order_id = 1

# 查询余票
def query_tickets(from_station, to_station, date):
    for ticket in tickets:
        if ticket["from_station"] == from_station and ticket["to_station"] == to_station and ticket["start_time"].startswith(date):
            print("车次：{}，出发时间：{}，到达时间：{}，价格：{}，成人票余票：{}，儿童票余票：{}".format(ticket["train_no"], ticket["start_time"], ticket["end_time"], ticket["price"], ticket["adult_num"], ticket["child_num"]))

# 购买车票
def buy_ticket(train_no, from_station, to_station, date, adult_num, child_num, name, id_card):
    global order_id
    for ticket in tickets:
        if ticket["train_no"] == train_no and ticket["from_station"] == from_station and ticket["to_station"] == to_station and ticket["start_time"].startswith(date):
            if ticket["adult_num"] >= adult_num and ticket["child_num"] >= child_num:
                ticket["adult_num"] -= adult_num
                ticket["child_num"] -= child_num
                order = {"order_id": order_id, "name": name, "id_card": id_card, "train_no": train_no, "from_station": from_station, "to_station": to_station, "date": date, "adult_num": adult_num, "child_num": child_num, "price": ticket["price"] * adult_num}
                order_id += 1
                for user in users:
                    if user["name"] == name and user["id_card"] == id_card:
                        user["order_history"].append(order)
                        break
                else:
                    user = {"name": name, "id_card": id_card, "order_history": [order]}
                    users.append(user)
                print("购票成功，订单号为：{}".format(order["order_id"]))
            else:
                print("余票不足，购票失败")

# 退票
def refund_ticket(order_id, name, id_card):
    for user in users:
        if user["name"] == name and user["id_card"] == id_card:
            for order in user["order_history"]:
                if order["order_id"] == order_id:
                    for ticket in tickets:
                        if ticket["train_no"] == order["train_no"] and ticket["from_station"] == order["from_station"] and ticket["to_station"] == order["to_station"] and ticket["start_time"].startswith(order["date"]):
                            ticket["adult_num"] += order["adult_num"]
                            ticket["child_num"] += order["child_num"]
                            user["order_history"].remove(order)
                            print("退票成功")
                            return
            else:
                print("订单不存在")
                return
    else:
        print("用户不存在")

# 查询订单
def query_order(order_id=None, name=None, id_card=None):
    if order_id:
        for user in users:
            for order in user["order_history"]:
                if order["order_id"] == order_id:
                    print("订单号：{}，姓名：{}，身份证号：{}，车次：{}，出发地：{}，目的地：{}，日期：{}，成人票数量：{}，儿童票数量：{}，价格：{}".format(order["order_id"], order["name"], order["id_card"], order["train_no"], order["from_station"], order["to_station"], order["date"], order["adult_num"], order["child_num"], order["price"]))
                    return
        else:
            print("订单不存在")
    elif name and id_card:
        for user in users:
            if user["name"] == name and user["id_card"] == id_card:
                for order in user["order_history"]:
                    print("订单号：{}，姓名：{}，身份证号：{}，车次：{}，出发地：{}，目的地：{}，日期：{}，成人票数量：{}，儿童票数量：{}，价格：{}".format(order["order_id"], order["name"], order["id_card"], order["train_no"], order["from_station"], order["to_station"], order["date"], order["adult_num"], order["child_num"], order["price"]))
                else:
                    print("该用户没有购买火车票")
            else:
                print("用户不存在")

# 测试
if __name__ == "__main__":
    # 查询余票
    query_tickets("北京", "上海", "2022-01-01")

    # 购买车票
    buy_ticket("G1234", "北京", "上海", "2022-01-01", 2, 1, "张三", "110101199001010001")

    # 退票
    refund_ticket(1, "张三", "110101199001010001")

    # 查询订单
    query_order(1)
    query_order(name="张三", id_card="110101199001010001")

这个示例实现了查询余票、购买车票、退票、查询订单等功能。你可以根据需求进行修改和扩展。