CODEWITHSUNDEEP
pythonloops
user5464440
user5464440

Reputation:

Using loops to compare two lists to find matching values

I have two lists, pPop and sPop. sPop is pPop after being sorted in ascending numerical order (they're populations of towns/cities).

I also have four other lists, pName, pType, pLat, and pLong, but I'm not really doing anything with them at this point in time.

I need to sort this list of cities by ascending population size, and I basically have been told to do it using what I know currently - which isn't that much. I've tried this using tuples and other stuff, but those fall under things I haven't been taught.

I have to compare sPop to pPop and use the information I get from that to reorder the other four lists, so I can spit them out in a .csv file.

I get the idea, I'm just not sure of the execution. I think I need to run a loop over all of sPop, with a loop inside that running for all pPop, which checks if sPop[x] = pPop[y], (x from 0 to len(sPop)) giving some kind of affirmative response when it's true. If it's true, then set pVar[y] equal to sVar[x].

After writing this out it seems fine, I'm just not entirely sure how to loop for every index in python. When I do, say,

for x in sPop

it's 

x = sPop[i] i=range(0:len(sPop))

when I'd prefer x to refer to the index itself, not the value of the array/list at that index.

Short version: loop over indices in an array with

for x in array

where x refers to the index. How do? If you can't, best way to refer to the index within a loop? It's late and my brain is fried on this problem after spending about six hours trying to work this out a few days ago using different methods.

EDIT:

Alright, got it. For anyone who is somehow curious (maybe someone'll stumble across this one in five years), you loop over sPop, then over pPop, (use for indexX, varX in enumerate(list) twice) then use

if varX ==varY
sortedList.append(initialList[varY])

Can't put down the actual code or I'd probably get smacked with a plagiarism checker.

Upvotes: 0

Views: 542

Answers (2)

John La Rooy
John La Rooy

Reputation: 304215

for x in range(len(sPop)):
    item = sPop[x]

Upvotes: 2

Hayley Guillou
Hayley Guillou

Reputation: 3973

To get the index:

for index, x in enumerate(sPop):
    print index, x

Upvotes: 2

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