用python代码写一个学生管理系统，连接sql sever数据库，并实现界面化以及实现以下功能：登录界面、显示学生的信息、对学生的信息实现增删改等

好的，下面是一个使用SQL Server数据库的学生管理系统的Python代码，使用pyodbc模块连接数据库，并使用Tkinter实现界面化：

import pyodbc
from tkinter import *

# 连接数据库
server = 'localhost'
database = 'students'
username = 'sa'
password = 'password'
conn = pyodbc.connect('DRIVER={SQL Server};SERVER='+server+';DATABASE='+database+';UID='+username+';PWD='+ password)
cursor = conn.cursor()

# 创建学生表
cursor.execute('''CREATE TABLE IF NOT EXISTS students
                  (id INT PRIMARY KEY IDENTITY,
                   name VARCHAR(50) NOT NULL,
                   age INT NOT NULL,
                   gender VARCHAR(10) NOT NULL)''')
conn.commit()

# 登录界面
def login():
    username = username_entry.get()
    password = password_entry.get()
    if username == 'admin' and password == 'password':
        show_students()
    else:
        messagebox.showerror("错误", "用户名或密码错误！")

# 添加学生信息
def add_student():
    name = name_entry.get()
    age = age_entry.get()
    gender = gender_entry.get()
    cursor.execute("INSERT INTO students (name, age, gender) VALUES (?, ?, ?)", (name, age, gender))
    conn.commit()
    show_students()

# 显示学生信息
def show_students():
    student_list.delete(0, END)
    cursor.execute("SELECT * FROM students")
    students = cursor.fetchall()
    for student in students:
        student_list.insert(END, student)

# 删除学生信息
def delete_student():
    selected_student = student_list.get(student_list.curselection())
    cursor.execute("DELETE FROM students WHERE id=?", (selected_student[0],))
    conn.commit()
    show_students()

# 修改学生信息
def update_student():
    selected_student = student_list.get(student_list.curselection())
    name = name_entry.get()
    age = age_entry.get()
    gender = gender_entry.get()
    cursor.execute("UPDATE students SET name=?, age=?, gender=? WHERE id=?", (name, age, gender, selected_student[0]))
    conn.commit()
    show_students()

# 创建界面
root = Tk()
root.title("学生管理系统")

username_label = Label(root, text="用户名")
username_label.grid(row=0, column=0)

password_label = Label(root, text="密码")
password_label.grid(row=1, column=0)

username_entry = Entry(root)
username_entry.grid(row=0, column=1)

password_entry = Entry(root, show="*")
password_entry.grid(row=1, column=1)

login_button = Button(root, text="登录", command=login)
login_button.grid(row=2, column=0, columnspan=2)

name_label = Label(root, text="姓名")
name_label.grid(row=3, column=0)

age_label = Label(root, text="年龄")
age_label.grid(row=4, column=0)

gender_label = Label(root, text="性别")
gender_label.grid(row=5, column=0)

name_entry = Entry(root)
name_entry.grid(row=3, column=1)

age_entry = Entry(root)
age_entry.grid(row=4, column=1)

gender_entry = Entry(root)
gender_entry.grid(row=5, column=1)

add_button = Button(root, text="添加", command=add_student)
add_button.grid(row=3, column=2)

delete_button = Button(root, text="删除", command=delete_student)
delete_button.grid(row=4, column=2)

update_button = Button(root, text="修改", command=update_student)
update_button.grid(row=5, column=2)

student_list = Listbox(root)
student_list.grid(row=6, column=0, columnspan=3)

root.mainloop()

# 关闭数据库连接
cursor.close()
conn.close()

在运行代码之前，请确保已经安装了pyodbc模块。运行后，程序将会创建一个名为“students”的SQL Server数据库，并创建一个名为“students”的表来存储学生信息。在登录界面中输入正确的用户名和密码后，您可以通过添加、删除和修改学生信息来测试该程序。