不能为多个项目更新购物车，对于单个项目可以正常工作，否则仅更新第一个项目

<!DOCTYPE html> <html lang="en"> <head>  <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">  <link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" rel="stylesheet">   <link href="/static/styles.css" rel="stylesheet"> <script src="https://code.jquery.com/jquery-3.3.1.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script> <script type="text/javascript" src="/path/to/jquery.js"></script> <script type="text/javascript" src="/path/to/jquery.jcarousel.js"> </script> </head> <body> <body> <form action="/updatecart" method="post"> {% for item in shoppingcart %} <div class="Tcard"> <div class='container2'> <p style="text-align:center">{{ item. name }}</p> <p class = "image"><img src= "{{ url_for('static', filename = item.image) }}" alt="Top 1" width ="100px" height = "100px"></p> <p class="price">Price: ${{ item.price }}</p> <label for="qty">Qty:</label> <select name = "qtydropdown" class = "qtydropdown" id = "mySelect" onchange='this.form.submit()'> <option value="{{ item.qty }}">{{ item.qty }}</option> <option value="0">0 - Remove</option> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> <option value="6">6</option> <option value="7">7</option> <option value="8">8</option> <option value="9">9</option> <option value="10">10</option> </select> <noscript><input type="submit" value="Submit"></noscript> <p class = "fontgrp">Size: {{ item.size }}</p> <p class = "fontgrp"><b>Total Cost: {{ item.total | usd }}</b></p> </div> </div> <div> <input id="productid" name="productid" type="hidden" value="{{ item.productid }}"> <input id="size" name="size" type="hidden" value="{{ item.size }}"> </div> {% endfor %} <div> <input class = "btn btn-primary" value = "Grand Total: {{ grandtotal | usd }}"> </div> <br> <div> <a href="/checkout" class="btn btn-primary" role="button" aria-pressed="true">Checkout</a>  </div> </form> </body> </html>

@app.route("/updatecart", methods = [ "POST"]) def updatecart(): if request.method == "POST": shoppingcart = db.execute("select * from cart1") #getting the qty from the html dropdown qtychanged = request.form.get("qtydropdown") # productid corresponding to the qty productid = request.form.get("productid") # size corresponding to the qty size = request.form.get("size") for rows in shoppingcart: if int(qtychanged) == 0: shoppingcart = db.execute("update cart1 set qty = :qty where productid = :productid and size = :size", productid = productid, size = size, qty = qtychanged) shoppingcart = db.execute("delete from cart1 where qty = :qty", qty = qtychanged) shoppingcart = db.execute("select * from cart1") if not shoppingcart: return apology("Cart is empty") if len(shoppingcart)!=0: shoppingcart = db.execute("select * from cart1 where productid = :productid and size = :size", productid = productid, size = size) shoppingcart = db.execute("update cart1 set qty = :qty where productid = :productid and size = :size", qty = qtychanged, productid = productid, size = size) shoppingcart = db.execute("select productid, name, size, qty, price, image, (qty * price) as total from cart1") if not shoppingcart: return apology("Cart is empty") grandtotal = 0 for row in shoppingcart: total = row["qty"] * float(row["price"]) grandtotal = grandtotal + total return render_template("testcartlayout.html", shoppingcart = shoppingcart, total = total, grandtotal = grandtotal)

1条回答

网友

1楼 · 发布于 2024-06-01 02:12:59

假设问题中的HTML工作正常，那么可以对Python代码进行一些改进，以确保它产生您想要的结果，或者至少提供一些指针

不需要SELECT所有行并在其上循环。使用SQL，您通常可以在一条语句中对所需的所有行进行操作
要确定购物车是否为空，使用SELECT COUNT(1) FROM cart1检索行数比检索所有行更有效，可以调用len
在DELETE的情况下，如果productid和size唯一地标识一行，那么delete it immediately using these criteria, there is no need to do an 首先更新`
如果删除了一行，则不需要进行进一步的更新，因此DELETE和UPDATE部分应位于if/else中
grandtotal可以在数据库中计算：SELECT SUM (qty * price) FROM cart1-无需SELECT和循环
total始终是为选择中的最后一行计算的total：这似乎不是很有用（如果我们在数据库中计算grandtotal，它就不会被计算）

下面的函数显示了如何改进现有方法。请注意：

我不知道你烧瓶设置的细节，所以这只是一个正常的功能；类似render_template和apology的烧瓶已被移除
我不知道db到底是什么：您可能需要调整查询结果的处理

def updatecart(qtychanged, productid, size):

    # SELECT COUNT to get the number of rows in the table
    # without retrieving all of them.
    result = db.execute("select count(1) from cart1")
    shoppingcart = result.fetchone()[0]
    # If the cart is empty there is no point trying to do anything
    if not shoppingcart:
        return "Cart is empty"

    if int(qtychanged) == 0:
        # Delete unwanted product from the cart.
        # Assuming productid and size uniquely identify an
        # item in the cart, just delete no need to update
        db.execute(
            "delete from cart1 where productid = :productid and size = :size",
            productid=productid,
            size=size,
        )
        # Apologise if the cart is empty
        result = db.execute("select count(1) from cart1")
        shoppingcart = result.fetchone()[0]
        if not shoppingcart:
            return "Cart is empty"
    else:
        # We're not deleting, so let's update.
        db.execute(
            "update cart1 set qty = :qty where productid = :productid and size = :size",
            qty=qtychanged,
            productid=productid,
            size=size,
        )
    shoppingcart = db.execute(
        "select productid, name, size, qty, price, image, (qty * price) as total from cart1"
    )

    # Declare total to avoid error in return
    # In the original code, total would be the total computed
    # for the last row in the cart, which doesn't seem useful.
    total = 0

    # Compute the total price
    res = db.execute("""SELECT SUM(qty * price) FROM cart1""")
    grandtotal = res.fetchone()[0]

    return shoppingcart, total, grandtotal

我编写了一些代码来测试这个函数：您可以通过将函数粘贴到一个文件中来运行它，将下面的代码粘贴到函数代码之后，然后调用python myfile——如果需要，您可以使用它进行实验。唯一的外部依赖项是sqlalchemy，我用它来模拟db

if __name__ == "__main__":
    import dqlalchemy as sa
    engine = sa.create_engine("sqlite://", echo=True)
    with engine.connect() as db:
        db.execute(
            """CREATE TABLE cart1 (
          productid INTEGER,
          name TEXT,
          size TEXT,
          qty INTEGER,
          price INTEGER,
          image TEXT
        )"""
        )
        ins = """INSERT INTO cart1
                 (productid, name, size, qty, price, image)
                 VALUES (?, ?, ?, ?, ?, ?)"""
        data = [
            (1, "Hat", "L", 1, 10, ""),
            (2, "Coat", "M", 5, 100, ""),
            (3, "Shirt", "M", 3, 20, ""),
        ]
        # Test 1: empty cart returns message
        db.execute(ins, data[0])
        res = updatecart(0, 1, "L")
        assert res == "Cart is empty", f"Expected empty message got {res}"
        # Reset the database
        db.execute("""DELETE FROM cart1""")
        # Test 2: update a row
        db.execute(ins, *data)
        # Buy two more hats
        resultobj, total, grandtotal = updatecart(3, 1, "L")
        rows = resultobj.fetchall()
        assert len(rows) == 3, f"Expected 3 got {len(rows)}"
        assert grandtotal == 590, f"Expected 590 got {grandtotal}"
        # Reset the database
        db.execute("""DELETE FROM cart1""")
        # Test 3: delete a row
        db.execute(ins, *data)
        # Remove the shirts
        resultobj, total, grandtotal = updatecart(0, 3, "M")
        rows = resultobj.fetchall()
        assert len(rows) == 2, f"Expected 2 got {len(rows)}"
        assert grandtotal == 510, f"Expected 510 got {grandtotal}"

相关问题更多 >

编程相关推荐

热门问题

热门文章