我在连接正在制作的书店GUI的前端和后端时遇到问题

到目前为止，我正在努力尝试使“搜索条目”功能正常工作，但是当我输入作者姓名时，它并没有显示我尝试搜索的条目，请记住，我只是想弄清楚为什么该条目未显示在列表框中。这是代码。能否请您找出问题所在？

前端：

from tkinter import *
import backend
window = Tk()


def view_command():
    ls1.delete(0,END)
    for row in backend.view():
        ls1.insert(END, row)

def search_command():
    ls1.delete(0,END)
    for row in backend.search(title_text.get(),year_text.get(),isbn_text.get()):
        ls1.insert(END,row)
        
    
    
#Labels

l1 = Label(window, text="Title")
l1.grid(row=0, column=0)

l2 = Label(window, text="Author")
l2.grid(row=0, column=2)

l3 = Label(window, text="Year")
l3.grid(row=1, column=0)

l4 = Label(window, text="ISBN")
l4 .grid(row=1, column=2)

#Entry boxes

title_text=StringVar()
e1 = Entry(window, textvariable=title_text)
e1.grid(row=0, column=1)

author_text=StringVar()
e2 = Entry(window, textvariable=author_text)
e2.grid(row=0, column=3)

year_text=StringVar()
e3 = Entry(window, textvariable=year_text)
e3.grid(row=1, column=1)

isbn_text=StringVar()
e4 = Entry(window, textvariable=isbn_text)
e4.grid(row=1, column=3)

#listbox

ls1 = Listbox(window, height=6,width=35)
ls1.grid(row=2, column=0, rowspan=6, columnspan=2)

#Scrollbar

scr1 = Scrollbar(window)
scr1.grid(row=2, column=2, rowspan=6)

#Making the scrolbar scroll down the listbox

ls1.configure(yscrollcommand=scr1.set)
scr1.configure(command=ls1.yview)

#Buttons and stuff

b1 = Button(window, text="View all", width=12, command=view_command)
b1.grid(row=2, column=3)
 
b2 = Button(window, text="Search Entry", width=12,command=search_command)
b2.grid(row=3, column=3)

b3 = Button(window, text="Add Entry", width=12)
b3.grid(row=4, column=3)

b4 = Button(window, text="Update Selected", width=12)
b4.grid(row=5, column=3)

b5 = Button(window, text="Delete Selected", width=12)
b5.grid(row=6, column=3)

b6 = Button(window, text="Exit", width=12)
b6.grid(row=7, column=3)
window.mainloop()

后端：

import sqlite3

def connect():
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("CREATE TABLE IF NOT EXISTS book (id INTEGER PRIMARY KEY, title text, author text, year integer, isbn integer)")
    con.commit()
    con.close()
   
def insert(title,author,year,isbn):
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("INSERT INTO book VALUES (NULL,?,?,?,?)",(title,author,year,isbn))
    con.commit()
    con.close()
    
def view():
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("SELECT * FROM book")
    rows=cr.fetchall()
    con.close()
    return rows
    
def search(title="",author="",year="",isbn=""):
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("SELECT * FROM book WHERE title=? OR author=? OR year=? OR isbn=?", (title, author, year, isbn))
    rows=cr.fetchall()
    con.close()
    return rows

def delete(id):
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("DELETE FROM book WHERE id=?",(id,))
    con.commit()
    con.close() 

def update(id, title, author, year, isbn):
    con=sqlite3.connect("books.db")
    cr=con.cursor()
    cr.execute("UPDATE book SET title=?, author=?, year=?, isbn=? WHERE id=?",(title,author,year,isbn,id))
    con.commit()
    con.close()

connect()
#insert("The Sun", "John Smith", 1918, 193123132)
#delete(3)
#zupdate(1, "The Moon", "John Smooth", 1917, 99999999)
#print(view())
print(search(author="John Smooth"))