Real-World Tasks With Dictionary Iteration

hello

I tried to test thed same as you have explained but i find the below

prices={'orange':4, 'apple': 3, 'banana':7}
for key in prices:
    prices[key] = prices[key] + 2
    print(prices)

output

{'orange': 6, 'apple': 3, 'banana': 7}
{'orange': 6, 'apple': 5, 'banana': 7}
{'orange': 6, 'apple': 5, 'banana': 9}

Why it is repeated 3 times?

Hellow

i follow the same example as you have explained but the output with some error

#inverse key with value
dic5={'red':7 ,"blue":8,"black":9 , "orange":22}
for key ,value  in dic5.items():
    dic5[value]=key
print(dic5)

output

Traceback (most recent call last): File “D:/Users/y.moneim/PycharmProjects/untitled2/Test002.py”, line 68, in <module> for key ,value in dic5.items(): RuntimeError: dictionary changed size during iteration

You put print(prices) inside your for loop which prints out the updated dictionary the number of times it was iterated over (3).

Try it like this:

prices={'orange':4, 'apple': 3, 'banana':7}
for key in prices:
    prices[key] = prices[key] + 2

print(prices)

Well said @joshengroff, and sorry to miss your comments @yasserkgl. The reason you’re seeing the error you mentioned above is because you’re iterating through your dictionary while changing it – this makes the Python runtime unsure of what items to include in the iteration. When you swap the keys and values in a dictionary, it’s normally much easier to make a new dictionary with the swapped items, like so:

d = {'a': 5, 'b': 6, 'c': 7}
swapped_d = {value: key for key, value in d.items()}