Why is my dictionary not being changed outside of my function

Question

Any changes that I make in products inside the function changeproducts is not being set outside of the function.

products = {
    "apple": {"price": 3.5, "stock": 134},
    "banana": {"price": 6.82, "stock": 52},
    "cake": {"price": 23, "stock": 5}
    }


def changeproducts():
    #operator enter new products
    items = input("Items: ").split()
    prices = map(float, input("Prices: ").split())
    stocks = map(int, input("Stocks: ").split())
    products = {
        item: {"price": price, "stock": stock} 
        for item, price, stock in zip(items, prices, stocks)
    }
    print (products)


changeproducts()
print(products)

Asked By: Goh Kian Seen

||

Source

Answer 1

Python functions can’t assign to variables in global scope by default, so it would be creating a new dictionary instead. Add global products to the top of the function:

def changeproducts():
  global products
  ...

Answered By: Toggle

Answer 2

As Toggle said, edits within a function only exist to that function or it’s sub-functions. You can either use a global variable as suggested,

def changeproducts():
    global products
    ...

But you can also use parameters + return values instead

def changeproducts(func_products):
    #use `func_products` instead of `products`
    ... 
    return func_products

products = changeproducts(products)
print(products)

When changeproducts is called, you give it the value of products, which it saves as func_products. Then once the function code has finished, it gives func_products as it’s return value. The return value is then saved into the products variable again

For more info, check the docs

Answered By: Cornelius-Figgle

Answer 3

Instead of reassigning the value, you can simply modify the list by using its update method, so in changeproducts do:

products.update(
    {
        item: {"price": price, "stock": stock}
        for item, price, stock in zip(items, prices, stocks)
    }
)

Answered By: Matiiss

Why is my dictionary not being changed outside of my function

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