如何检查嵌套在循环中的字典中是否存在值

Question

I am trying to increment the quanitity value if the item name is already in the dictionary nested within a list, the method I was planning on using is by checking if itemname doesn't already exists in the dictionary then add to the list, else if it does exist in the dictionary then update thw quantity by one.

I'm not too sure how to check to see if the itemname is in the nested dictionary iv'e looked around but haven't found anything

@app.route("/AddToCart", methods=["POST", "GET"])
def addToCart():
    itemId = int(request.form.get("productId"))
    MenuItem = Menu.query.get(itemId)

    if MenuItem is None:
        return render_template("error.html", errorMessage="There has been an issue adding this item to your basket")

    sVars = session['cart']

    if(MenuItem.ItemName not in sVars):
        sVars.append({'Itemname': MenuItem.ItemName, 'Itemprice': float(MenuItem.ItemPrice), 'Qty': 0})
    else:
        sVars['Qty'] += 1

    session['cart'] = sVars

    allPrices = Money(amount=sum([x['Itemprice'] for x in sVars]), currency='GBP')

    return render_template("cart.html", cartSession=session['cart'],allPrices=allPrices)

Answer 1

Hi this is work for me

def check_exist(my_dict, key):
    if key in my_dict.keys():
        return True
    return False

Answer 2

One easy way to do this would be to replace this section of code:

    sVars = session['cart']

    if(MenuItem.ItemName not in sVars):
        sVars.append({'Itemname': MenuItem.ItemName, 'Itemprice': float(MenuItem.ItemPrice), 'Qty': 0})
    else:
        sVars['Qty'] += 1

    session['cart'] = sVars

    allPrices = Money(amount=sum([x['Itemprice'] for x in sVars]), currency='GBP')

    return render_template("cart.html", cartSession=session['cart'],allPrices=allPrices)

with:

    cart = session['cart']
    for item in cart:
        if item['Itemname'] == MenuItem.ItemName:
            item['Qty'] += 1
            break
    else:
        cart.append({
            'Itemname': MenuItem.ItemName,
            'Itemprice': float(MenuItem.ItemPrice),
            'Qty': 1
        })

    totalPrice = Money(
        amount=sum([item['Itemprice'] * item['Qty'] for item in cart]), 
        currency='GBP')

    return render_template("cart.html", cartSession=cart, allPrices=totalPrice)

Some notes: First, your original code tries to use sVars both as an array (with .append() ) and as a dictionary (with sVars['Qty'] ). It has to be one or the other, of course. I am assuming that it is an array, but correct me if that assumption is wrong (and show an example of it).

Second, my suggested code uses a Python feature that many are unfamiliar with, an else block with a for loop. If you haven't see this before, it's designed for just this kind of use. The way it works is that if the loop is explicitly exited with a break statement, the else block is not executed. If the loop runs to completion, then the else block is executed.

Finally, I assume that allPrices should be the total price of all items in the cart, so each item's price should be multiplied by its quantity.

Answer 3

assuming you have a list like this:

ls = [{"Itemname": "Test", "Itemprice": 1, "Qty": 0}, {"Itemname": "Test1", "Itemprice": 1, "Qty": 0}]

then you could have a function like this to update the items:

def updateItems(inpdic):
    for item in ls:
        if item["Itemname"] == inpdic["Itemname"]:
            item["Qty"] += 1
            return
    ls.append(inpdic)

you go over all the items in the list, if an item with the same name exists you increase the quantity and exit, otherwise you append it.

Answer 4

sVars=[]


flag=0
indexgot=0

for i in sVars:
    if(i['Itemname']=='item1'):
        flag=1
        indexgot=i


if(not flag):
    sVars.append({'Itemname': "item1", 'Itemprice': float(50), 'Qty': 0})
else:
    sVars[sVars.index(indexgot)]['Qty'] += 1

print(sVars)

just an approach ... to solve your problem.