Thank you so much for the help, and the example!
So, by putting quotes around a dict key, like so dict["key"] or in my case
cart["item"] this makes the dict have ONE key. The loop assigns the
cart_items to this ONE key until the end of the loop, and I'm left with
{'item': 5}. . .
Where as if you do NOT put the key in quotes, dict[key] or cart[item], this
basically means the dict has as many keys as you're iterating through. In
other words it assigns the cart_item as a key and a value, and saves them
all to the dict.
Is that correct?
On Tue, May 17, 2016 at 5:01 AM, <c...@zip.com.au> wrote:
> On 17May2016 04:28, Chris Kavanagh <cka...@gmail.com> wrote:
>
>> Could someone tell me why this different behavior occurs between these 2
>> code snippets, please. The 1st example has quotes around it ['item'] only
>> adds the last item to the dict (cart). In the 2nd example the item does
>> not
>> have quotes around it [item] and every entry is added to the dict.
>>
>> Why?
>>
> [...]
>
>> # Example #1
>> cart_items = ['1','2','3','4','5']
>> cart = {}
>> for item in cart_items:
>> cart['item'] = item
>>
>
> This for loop assigns the values '1','2','3','4','5' in succession to the
> variable named "item". Then the body of the loop assigns that value (via
> the variable "item") to the single dictionary slot with the fixed key with
> string value 'item' i.e. always the same slot. And the last item is the
> one kept. All the earlier assignments are overwritten by the later ones:
> they happen, but are replaced.
>
> print cart
>> #output
>> {'item': 5}
>>
>
> Which you see above.
>
> # Example #2
>> cart_items = ['1','2','3','4','5']
>> cart = {}
>> for item in cart_items:
>> cart[item] = item
>>
>
> Here, the variable named "item" takes on the values as before, but the
> diction slot chosen also comes form that variable. So each value ends up in
> its own slot as your output shows.
>
> print cart
>> # output
>> {'1': '1', '3': '3', '2': '2', '5': '5', '4': '4'}
>>
>
> The essential difference here is that in the first example the expression
> for the slot in the dictionary is the expression:
>
> 'item'
>
> which is simply the fixed string 'item'. In the second example the
> expression is:
>
> item
>
> which produces the current value stored in the variable "item".
>
> Cheers,
> Cameron Simpson <c...@zip.com.au>
>
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