Get last tuple from two-dimensional array?

[Winfried]

Hello,

Searching the archives with "two dimensional array last" returned no hits.

I need to find the last tuple from this kind of output:

[[2.3110949921647266, 48.81514649393979], [2.3113524842301563, 48.815923619981966], …[2.28392243385315, 48.84728589885864], [2.2819232977235515, 48.84809311844251]]

Is there a better way than this?

first = track['geometry']['coordinates'][0]

#BAD last = track['geometry']['coordinates'][-1]
#BAD last = track['geometry']['coordinates'].keys()[-1]
#BAD last = track['geometry']['coordinates'].count()
sizearray = len(track['geometry']['coordinates'])
print(track['geometry']['coordinates'][sizearray-1])

Thank you.

[Gribouillis]

What is the result of

print(type(track['geometry']['coordinates']))

?

[buran]

in Python you can use negative indexes
just

print(track['geometry']['coordinates'][-1])

by the way, this is list of lists, not lists of tuples. Although they look pretty much the same, lists are mutable, and tuples are not.
this is list [1, 2, 3]
and this is tuple (1, 2, 3)

[Winfried]

Thanks for the info about list of lists vs. list of tuples.

>> print(type(track['geometry']['coordinates']))
<class 'list'>

>> print(track['geometry']['coordinates'][-1])
[2.2819232977235515, 48.84809311844251]

Odd: This time, "[-1]" worked

[buran]

Odd: This time, "[-1]" worked

when was it not working?

[Winfried]

In the original post:

#BAD last = track['geometry']['coordinates'][-1]

It returned an error, which is why I used the less elegant "sizearray-1".

Maybe it was a typo I didn't catch.

---

Another issue I came accross: In the JSON input file, most of the tracks are LineString, but a few of them are crappy Multilinestring (I guess the user's GPS burped at that point), so the code breaks because it ends up querying Nominatim with wrong data:

INPUT
GOOD : [2.3646783828735356, 48.844165146100025]
BAD : [[2.378497123718262, 48.85067473135253], [2.376008033752442, 48.85138776898278]]

import geojson
from geopy.geocoders import Nominatim

…

coords = track['geometry']['coordinates'][0]
#Flip coords: Nominatim expects lat, lon
coords = coords[::-1]
location = "{}, {}".format(coords[0], coords[1])

geolocator = Nominatim(user_agent="my-application",timeout=3)
location = geolocator.reverse(location)
try:
    return(location.raw['address']['town'])
except KeyError:
    return(location.raw['address']['city'])

In this particular case, it doesn't matter if there's a straight line all of a sudden between two coords, so, as a work-around, I was wondering if there's a way to turn Multilinestring into Linestring?

[buran]

Can you show small input file in full, with both good and bad data. LineString, MultilineString???
if you have list(array) of coordinates which one is the correct, according to you?