用Python编写一个学生信息管理系统(姓名、学号、联系方式、绩点)，主要包含两个界面：登录界面和学生信息管理系统，学生信息管理系统主要功能是实现学生信息的增删改查。Python的图形界面GUI工具有很多，Tkinter和PyQt5可以任选其一。

好的，下面是一个基于Tkinter的学生信息管理系统的代码示例：

import tkinter as tk

class StudentInfo:
    def __init__(self, name, id, contact, score):
        self.name = name
        self.id = id
        self.contact = contact
        self.score = score

class StudentInfoManager:
    def __init__(self):
        self.student_infos = []
    
    def add_student_info(self, student_info):
        self.student_infos.append(student_info)
    
    def remove_student_info(self, id):
        for student_info in self.student_infos:
            if student_info.id == id:
                self.student_infos.remove(student_info)
                return True
        return False
    
    def update_student_info(self, id, new_student_info):
        for i, student_info in enumerate(self.student_infos):
            if student_info.id == id:
                self.student_infos[i] = new_student_info
                return True
        return False
    
    def find_student_info(self, id):
        for student_info in self.student_infos:
            if student_info.id == id:
                return student_info
        return None

class LoginPanel(tk.Frame):
    def __init__(self, parent, student_info_manager, on_login):
        super().__init__(parent)
        self.student_info_manager = student_info_manager
        self.on_login = on_login
        
        self.username_label = tk.Label(self, text="Username:")
        self.username_entry = tk.Entry(self)
        self.password_label = tk.Label(self, text="Password:")
        self.password_entry = tk.Entry(self, show="*")
        self.login_button = tk.Button(self, text="Login", command=self.login)
        
        self.username_label.pack()
        self.username_entry.pack()
        self.password_label.pack()
        self.password_entry.pack()
        self.login_button.pack()
    
    def login(self):
        if self.username_entry.get() == "admin" and self.password_entry.get() == "admin":
            self.on_login()
        else:
            tk.messagebox.showerror("Error", "Incorrect username or password")

class StudentInfoPanel(tk.Frame):
    def __init__(self, parent, student_info_manager):
        super().__init__(parent)
        self.student_info_manager = student_info_manager
        
        self.id_label = tk.Label(self, text="ID:")
        self.id_entry = tk.Entry(self)
        self.name_label = tk.Label(self, text="Name:")
        self.name_entry = tk.Entry(self)
        self.contact_label = tk.Label(self, text="Contact:")
        self.contact_entry = tk.Entry(self)
        self.score_label = tk.Label(self, text="Score:")
        self.score_entry = tk.Entry(self)
        self.add_button = tk.Button(self, text="Add", command=self.add_student_info)
        self.remove_button = tk.Button(self, text="Remove", command=self.remove_student_info)
        self.update_button = tk.Button(self, text="Update", command=self.update_student_info)
        self.find_button = tk.Button(self, text="Find", command=self.find_student_info)
        
        self.id_label.pack()
        self.id_entry.pack()
        self.name_label.pack()
        self.name_entry.pack()
        self.contact_label.pack()
        self.contact_entry.pack()
        self.score_label.pack()
        self.score_entry.pack()
        self.add_button.pack()
        self.remove_button.pack()
        self.update_button.pack()
        self.find_button.pack()
    
    def add_student_info(self):
        student_info = StudentInfo(self.name_entry.get(), self.id_entry.get(), self.contact_entry.get(), self.score_entry.get())
        self.student_info_manager.add_student_info(student_info)
        tk.messagebox.showinfo("Info", "Student info added successfully")
    
    def remove_student_info(self):
        success = self.student_info_manager.remove_student_info(self.id_entry.get())
        if success:
            tk.messagebox.showinfo("Info", "Student info removed successfully")
        else:
            tk.messagebox.showerror("Error", "Student info not found")
    
    def update_student_info(self):
        new_student_info = StudentInfo(self.name_entry.get(), self.id_entry.get(), self.contact_entry.get(), self.score_entry.get())
        success = self.student_info_manager.update_student_info(self.id_entry.get(), new_student_info)
        if success:
            tk.messagebox.showinfo("Info", "Student info updated successfully")
        else:
            tk.messagebox.showerror("Error", "Student info not found")
    
    def find_student_info(self):
        student_info = self.student_info_manager.find_student_info(self.id_entry.get())
        if student_info:
            self.name_entry.delete(0, tk.END)
            self.contact_entry.delete(0, tk.END)
            self.score_entry.delete(0, tk.END)
            self.name_entry.insert(0, student_info.name)
            self.contact_entry.insert(0, student_info.contact)
            self.score_entry.insert(0, student_info.score)
        else:
            tk.messagebox.showerror("Error", "Student info not found")

class StudentInfoManagementSystem(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Student Info Management System")
        self.geometry("400x300")
        
        self.student_info_manager = StudentInfoManager()
        
        self.login_panel = LoginPanel(self, self.student_info_manager, self.show_student_info_panel)
        self.student_info_panel = StudentInfoPanel(self, self.student_info_manager)
        
        self.login_panel.pack(fill=tk.BOTH, expand=True)
    
    def show_student_info_panel(self):
        self.login_panel.pack_forget()
        self.student_info_panel.pack(fill=tk.BOTH, expand=True)

if __name__ == "__main__":
    app = StudentInfoManagementSystem()
    app.mainloop()

这个程序中，我们定义了一个`StudentInfo`类来表示学生信息，包含姓名、学号、联系方式和绩点四个属性。另外我们还定义了一个`StudentInfoManager`类来管理所有学生信息，包含增加、删除、修改和查找等操作。这些操作都是通过对`student_infos`列表进行操作实现的。

程序的图形界面包含两个部分，一个是登录界面`LoginPanel`，另一个是学生信息管理界面`StudentInfoPanel`。在登录界面中，我们使用了`tk.Entry`来输入用户名和密码，并在点击`Login`按钮时判断用户名和密码是否正确。如果正确，则调用`on_login`方法切换到学生信息管理界面；如果不正确，则弹出错误提示框。在学生信息管理界面中，我们使用了`tk.Entry`来输入学生信息的各个属性，并使用`tk.Button`来触发各种操作。其中，增加、删除、修改和查找操作都是通过调用`StudentInfoManager`中相应的方法实现的。在查找操作中，我们可以根据学号来查找学生信息，并在找到后把学生信息的各个属性填入对应的`tk.Entry`中。

以上就是一个简单的基于Tkinter的学生信息管理系统的代码示例。注意，这个示例只是一个参考，实际情况下可能需要根据具体需求进行修改。