Python写一个高铁购票系统，有一等座，二等座，有车次，有登录注册系统，有余票，可以改签和退票，有订单详情，

好的，这是一个比较复杂的系统，需要分多个模块实现。下面是一个大致的代码框架，你可以在此基础上进行开发。

## 1. 登录注册系统

首先需要实现一个登录注册系统，用于用户身份验证和管理。可以使用MySQL等数据库进行存储和查询用户信息。

import mysql.connector

# 连接数据库
mydb = mysql.connector.connect(
  host="localhost",
  user="yourusername",
  password="yourpassword",
  database="mydatabase"
)

# 注册功能
def register(username, password):
    mycursor = mydb.cursor()
    sql = "INSERT INTO users (username, password) VALUES (%s, %s)"
    val = (username, password)
    mycursor.execute(sql, val)
    mydb.commit()

# 登录功能
def login(username, password):
    mycursor = mydb.cursor()
    sql = "SELECT * FROM users WHERE username = %s AND password = %s"
    val = (username, password)
    mycursor.execute(sql, val)
    user = mycursor.fetchone()
    if user is not None:
        return True
    else:
        return False

## 2. 购票系统

实现购票系统需要考虑到多个因素，如余票、车次等。可以将车次信息存储在数据库中，每次购票时更新余票数量。

# 连接数据库
mydb = mysql.connector.connect(
  host="localhost",
  user="yourusername",
  password="yourpassword",
  database="mydatabase"
)

# 获取车次信息
def get_train_info(train_no):
    mycursor = mydb.cursor()
    sql = "SELECT * FROM trains WHERE train_no = %s"
    val = (train_no,)
    mycursor.execute(sql, val)
    train_info = mycursor.fetchone()
    return train_info

# 购票功能
def buy_ticket(train_no, seat_type, user_id):
    train_info = get_train_info(train_no)
    if train_info is None:
        return "该车次不存在"
    if seat_type == "1st":
        if train_info[2] <= 0:
            return "一等座已售完"
        else:
            sql = "UPDATE trains SET 1st_seat = %s WHERE train_no = %s"
            val = (train_info[2]-1, train_no)
    else:
        if train_info[3] <= 0:
            return "二等座已售完"
        else:
            sql = "UPDATE trains SET 2nd_seat = %s WHERE train_no = %s"
            val = (train_info[3]-1, train_no)
    mycursor = mydb.cursor()
    mycursor.execute(sql, val)
    mydb.commit()
    # 保存订单信息
    sql = "INSERT INTO orders (train_no, seat_type, user_id) VALUES (%s, %s, %s)"
    val = (train_no, seat_type, user_id)
    mycursor.execute(sql, val)
    mydb.commit()
    return "购票成功"

## 3. 改签和退票

改签和退票功能与购票类似，只需更新余票数量或删除订单即可。

# 改签功能
def change_ticket(order_id, train_no, seat_type):
    train_info = get_train_info(train_no)
    if train_info is None:
        return "该车次不存在"
    if seat_type == "1st":
        if train_info[2] <= 0:
            return "一等座已售完"
        else:
            sql = "UPDATE trains SET 1st_seat = %s WHERE train_no = %s"
            val = (train_info[2]-1, train_no)
    else:
        if train_info[3] <= 0:
            return "二等座已售完"
        else:
            sql = "UPDATE trains SET 2nd_seat = %s WHERE train_no = %s"
            val = (train_info[3]-1, train_no)
    mycursor = mydb.cursor()
    mycursor.execute(sql, val)
    mydb.commit()
    # 更新订单信息
    sql = "UPDATE orders SET train_no = %s, seat_type = %s WHERE id = %s"
    val = (train_no, seat_type, order_id)
    mycursor.execute(sql, val)
    mydb.commit()
    return "改签成功"

# 退票功能
def refund_ticket(order_id):
    mycursor = mydb.cursor()
    # 获取订单信息
    sql = "SELECT * FROM orders WHERE id = %s"
    val = (order_id,)
    mycursor.execute(sql, val)
    order_info = mycursor.fetchone()
    if order_info is None:
        return "该订单不存在"
    train_no = order_info[1]
    seat_type = order_info[2]
    # 更新余票数量
    train_info = get_train_info(train_no)
    if seat_type == "1st":
        sql = "UPDATE trains SET 1st_seat = %s WHERE train_no = %s"
        val = (train_info[2]+1, train_no)
    else:
        sql = "UPDATE trains SET 2nd_seat = %s WHERE train_no = %s"
        val = (train_info[3]+1, train_no)
    mycursor.execute(sql, val)
    mydb.commit()
    # 删除订单
    sql = "DELETE FROM orders WHERE id = %s"
    val = (order_id,)
    mycursor.execute(sql, val)
    mydb.commit()
    return "退票成功"

## 4. 订单详情

订单详情可以查询用户的订单信息，并显示相应的车次和座位类型。

# 订单详情功能
def get_order_info(user_id):
    mycursor = mydb.cursor()
    sql = "SELECT orders.id, trains.train_no, orders.seat_type FROM orders INNER JOIN trains ON orders.train_no = trains.train_no WHERE user_id = %s"
    val = (user_id,)
    mycursor.execute(sql, val)
    orders = mycursor.fetchall()
    for order in orders:
        print("订单号：", order[0])
        print("车次：", order[1])
        print("座位类型：", order[2])

以上是一个简单的高铁购票系统的代码框架，你可以根据自己的需求进行修改和完善。