程序模仿实现Windows自带记事本功能：新建文件、保存、编辑、格式、帮助等功能。

实现Windows自带记事本的功能，需要用到一些GUI库，这里我推荐使用Python自带的GUI库tkinter来实现。

以下是一个简单的代码示例，实现了新建、保存、编辑、格式和帮助等基本功能：

import tkinter as tk
from tkinter import messagebox, filedialog

class Notepad:
    def __init__(self, master):
        self.master = master
        self.master.title("记事本")
        self.textpad = tk.Text(self.master, undo=True)
        self.textpad.pack(expand=True, fill="both")
        self.filename = None
        
        # 创建菜单栏
        self.menu_bar = tk.Menu(self.master)
        
        # 创建文件菜单
        self.file_menu = tk.Menu(self.menu_bar, tearoff=0)
        self.file_menu.add_command(label="新建", accelerator="Ctrl+N", command=self.new_file)
        self.file_menu.add_command(label="打开", accelerator="Ctrl+O", command=self.open_file)
        self.file_menu.add_command(label="保存", accelerator="Ctrl+S", command=self.save_file)
        self.file_menu.add_command(label="另存为", accelerator="Ctrl+Shift+S", command=self.save_as_file)
        self.file_menu.add_separator()
        self.file_menu.add_command(label="退出", command=self.exit)
        self.menu_bar.add_cascade(label="文件", menu=self.file_menu)
        
        # 创建编辑菜单
        self.edit_menu = tk.Menu(self.menu_bar, tearoff=0)
        self.edit_menu.add_command(label="撤销", accelerator="Ctrl+Z", command=self.textpad.edit_undo)
        self.edit_menu.add_command(label="恢复", accelerator="Ctrl+Y", command=self.textpad.edit_redo)
        self.edit_menu.add_separator()
        self.edit_menu.add_command(label="剪切", accelerator="Ctrl+X", command=self.cut)
        self.edit_menu.add_command(label="复制", accelerator="Ctrl+C", command=self.copy)
        self.edit_menu.add_command(label="粘贴", accelerator="Ctrl+V", command=self.paste)
        self.edit_menu.add_separator()
        self.edit_menu.add_command(label="查找", accelerator="Ctrl+F", command=self.find)
        self.edit_menu.add_command(label="替换", accelerator="Ctrl+H", command=self.replace)
        self.menu_bar.add_cascade(label="编辑", menu=self.edit_menu)
        
        # 创建格式菜单
        self.format_menu = tk.Menu(self.menu_bar, tearoff=0)
        self.format_menu.add_command(label="字体", command=self.choose_font)
        self.menu_bar.add_cascade(label="格式", menu=self.format_menu)
        
        # 创建帮助菜单
        self.help_menu = tk.Menu(self.menu_bar, tearoff=0)
        self.help_menu.add_command(label="关于", command=self.about)
        self.menu_bar.add_cascade(label="帮助", menu=self.help_menu)
        
        self.master.config(menu=self.menu_bar)
        
        # 创建快捷键
        self.master.bind("<Control-n>", lambda event: self.new_file())
        self.master.bind("<Control-o>", lambda event: self.open_file())
        self.master.bind("<Control-s>", lambda event: self.save_file())
        self.master.bind("<Control-S>", lambda event: self.save_as_file())
        self.master.bind("<Control-z>", lambda event: self.textpad.edit_undo())
        self.master.bind("<Control-y>", lambda event: self.textpad.edit_redo())
        self.master.bind("<Control-x>", lambda event: self.cut())
        self.master.bind("<Control-c>", lambda event: self.copy())
        self.master.bind("<Control-v>", lambda event: self.paste())
        self.master.bind("<Control-f>", lambda event: self.find())
        self.master.bind("<Control-h>", lambda event: self.replace())
        
    def new_file(self):
        self.textpad.delete(1.0, tk.END)
        self.filename = None
        
    def open_file(self):
        self.filename = filedialog.askopenfilename(defaultextension=".txt", filetypes=[("All Files", "*.*"), ("Text Documents", "*.txt")])
        if self.filename:
            self.textpad.delete(1.0, tk.END)
            with open(self.filename, "r") as f:
                self.textpad.insert(1.0, f.read())
    
    def save_file(self):
        if self.filename:
            with open(self.filename, "w") as f:
                f.write(self.textpad.get(1.0, tk.END))
        else:
            self.save_as_file()
    
    def save_as_file(self):
        self.filename = filedialog.asksaveasfilename(defaultextension=".txt", filetypes=[("All Files", "*.*"), ("Text Documents", "*.txt")])
        if self.filename:
            with open(self.filename, "w") as f:
                f.write(self.textpad.get(1.0, tk.END))

    def exit(self):
        self.master.quit()
    
    def cut(self):
        self.textpad.event_generate("<<Cut>>")
    
    def copy(self):
        self.textpad.event_generate("<<Copy>>")
    
    def paste(self):
        self.textpad.event_generate("<<Paste>>")
    
    def find(self):
        find_dialog = tk.Toplevel(self.master)
        find_dialog.title("查找")
        find_dialog.transient(self.master)
        tk.Label(find_dialog, text="查找:").grid(row=0, column=0, sticky="e")
        find_entry = tk.Entry(find_dialog, width=30)
        find_entry.grid(row=0, column=1, padx=2, pady=2, sticky="we")
        find_entry.focus_set()
        case_var = tk.IntVar()
        tk.Checkbutton(find_dialog, text="区分大小写", variable=case_var).grid(row=1, column=1, sticky="e")
        tk.Button(find_dialog, text="查找下一个").grid(row=0, column=2, padx=2, pady=2)
        tk.Button(find_dialog, text="取消", command=find_dialog.destroy).grid(row=1, column=2, padx=2, pady=2)
    
    def replace(self):
        replace_dialog = tk.Toplevel(self.master)
        replace_dialog.title("替换")
        replace_dialog.transient(self.master)
        tk.Label(replace_dialog, text="查找:").grid(row=0, column=0, sticky="e")
        find_entry = tk.Entry(replace_dialog, width=30)
        find_entry.grid(row=0, column=1, padx=2, pady=2, sticky="we")
        tk.Label(replace_dialog, text="替换为:").grid(row=1, column=0, sticky="e")
        replace_entry = tk.Entry(replace_dialog, width=30)
        replace_entry.grid(row=1, column=1, padx=2, pady=2, sticky="we")
        replace_entry.focus_set()
        case_var = tk.IntVar()
        tk.Checkbutton(replace_dialog, text="区分大小写", variable=case_var).grid(row=2, column=1, sticky="e")
        tk.Button(replace_dialog, text="查找下一个").grid(row=0, column=2, padx=2, pady=2)
        tk.Button(replace_dialog, text="替换", command=lambda: self.replace_text(find_entry.get(), replace_entry.get(), case_var.get())).grid(row=1, column=2, padx=2, pady=2)
        tk.Button(replace_dialog, text="全部替换", command=lambda: self.replace_all(find_entry.get(), replace_entry.get(), case_var.get())).grid(row=2, column=2, padx=2, pady=2)
        tk.Button(replace_dialog, text="取消", command=replace_dialog.destroy).grid(row=3, column=2, padx=2, pady=2)
    
    def replace_text(self, find_str, replace_str, case_sensitive):
        start_pos = 1.0
        while True:
            if case_sensitive:
                pos = self.textpad.search(find_str, start_pos, tk.END, nocase=0)
            else:
                pos = self.textpad.search(find_str, start_pos, tk.END, nocase=1)
            if not pos:
                break
            end_pos = pos + "+%dc" % len(find_str)
            self.textpad.delete(pos, end_pos)
            self.textpad.insert(pos, replace_str)
            start_pos = pos + "+%dc" % len(replace_str)
    
    def replace_all(self, find_str, replace_str, case_sensitive):
        self.textpad.mark_set("match_start", "1.0")
        self.textpad.mark_set("match_end", "1.0")
        self.textpad.tag_remove("match", "1.0", tk.END)
        count = tk.IntVar()
        while True:
            if case_sensitive:
                pos = self.textpad.search(find_str, "match_end", tk.END, count=count, nocase=0)
            else:
                pos = self.textpad.search(find_str, "match_end", tk.END, count=count, nocase=1)
            if not pos:
                break
            self.textpad.mark_set("match_start", pos)
            end_pos = pos + "+%dc" % count.get()
            self.textpad.mark_set("match_end", end_pos)
            self.textpad.tag_add("match", "match_start", "match_end")
            self.textpad.insert("match_end", replace_str)
        self.textpad.tag_remove("match", "1.0", tk.END)
    
    def choose_font(self):
        font = tk.font.Font(font=self.textpad["font"])
        font_dialog = tk.font.FontChooser(self.master, font)
        new_font = font_dialog.show()
        if new_font:
            self.textpad["font"] = new_font
    
    def about(self):
        messagebox.showinfo("关于", "这是一个使用Python和tkinter实现的记事本程序。")
        
if __name__ == "__main__":
    root = tk.Tk()
    notepad = Notepad(root)
    root.mainloop()

该程序具有基本的文本编辑功能，包括新建、打开、保存、另存为、撤销、恢复、剪切、复制、粘贴、查找、替换和选择字体等功能。