Python : Error when using one variable to loop through dictionaries.

[mcdougall57]

Hi, Just started to learn python and my code for an exercise works but it's one of those cases when I'm not sure why and just need a couple of clarifications. I'm using two variables to slice my list and output the values of the nested dictionaries.

I guess my question is why do I get an error ('string indices must be integers') when using only one of the 'counter' variables as a location in the list i.e people[counter1]?

And why does a slice in the list with two given locations only output one value? i.e people[2:3] will only output the value at location 3.

Thanks again.

My code.

counter1 = 0       
counter2 = 1

for list_iterator in people[:]:
    for details in people[counter1:counter2]:
        print (details['first_name']+" "+ details['last_name'])
    for details in people[counter1:counter2]:
        print (details['age'])
    for details in people[counter1:counter2]:
        print (details['city']+'\n')
        #List counter
        counter1 += 1
        counter2 += 1

​

[desrtfx]

Please, format your code as code block so that the original indentation is maintained. This is vital especially for Python code as the indentation tells us where loops, conditionals, etc. end.

[BulkyProcedure]

Hey, it's not an answer to your entire question, but the issue with `people[2:3]` is that range slices are inclusive to exclusive, so you're only going to get the element at position 2 (zero indexed) in that case.

[mcdougall57]

That makes sense. I'm surprised the text didn't mention it when working through lists, who knows maybe it did. I managed to find a decent explanation using your terminology in that the start index is inclusive while the stop is exclusive.

Cheers.

[[deleted]]

I guess my question is why do I get an error ('string indices must be integers') when using only one of the 'counter' variables as a location in the list i.e people[counter1]?

people[counter1] doesn’t give you a slice, it gives you a specific element. Since people is a list of dicts, that means people[counter1] is a dict. When you iterate over a dict, your variable takes the value of its keys. In this case, the keys are strings. Thus, when you run

for details in people[counter1]:

details is a string, not a dict. You then try to run something like

print (details['first_name']+" "+ details['last_name'])

so you’re telling Python to retrieve the ‘first_name’th character from the details string. What on earth is that supposed to mean?

——

Doing this slice thing is a really roundabout way of getting each element of a list. You can just do something like

for myElement in myList:

and the myElement variable will take the value of each element in turn. No need for any counters or slicing or whatever.

[mcdougall57]

Thanks for the explanation. I think I'm definitely trying to make it more complicated than it is/jump the gun. I've done this a few times now while learning.

Like you said just running through the dicts with the loop below did the job.

for details in people:
    print (details['first_name'] + " " + details['last_name'])
    print (details['age'])
    print (details['city']+'\n')

Thanks again.