Is there a better way to iterate over two lists, getting one element from each list for each iteration?

python list iteration
chongman picture chongman · Dec 17, 2009 · Viewed 159k times · Source

I have a list of Latitudes and one of Longitudes and need to iterate over the latitude and longitude pairs.

Is it better to:

  • A. Assume that the lists are of equal lengths:

    for i in range(len(Latitudes)):
    Lat,Long=(Latitudes[i],Longitudes[i])

  • B. Or:

    for Lat,Long in [(x,y) for x in Latitudes for y in Longitudes]:

(Note that B is incorrect. This gives me all the pairs, equivalent to itertools.product())

Any thoughts on the relative merits of each, or which is more pythonic?

Answer

Roberto Bonvallet picture Roberto Bonvallet · Dec 17, 2009

This is as pythonic as you can get:

for lat, long in zip(Latitudes, Longitudes):
    print(lat, long)

Related questions

How do I loop through a list by twos?

I want to loop through a Python list and process 2 list items at a time. Something like this in another language: for(int i = 0; i < list.length(); i+=2) { // do something with list[i] and list[i + 1] } What's the best …

Read More
Python using enumerate inside list comprehension

Lets suppose I have a list like this: mylist = ["a","b","c","d"] To get the values printed along with their index I can use Python's enumerate function like this >>> for i,j in enumerate(mylist): ... print …

Read More
Python list iterator behavior and next(iterator)

Consider: >>> lst = iter([1,2,3]) >>> next(lst) 1 >>> next(lst) 2 So, advancing the iterator is, as expected, handled by mutating that same object. This being the case, I would expect: a = iter(list(range(10))) …

Read More