How do I pass parameters to a Python function?

Question

I am trying to use this function found online to calculate the distance between two latitude and longitude points on the Earth.

However, I do not know how to pass my values for latitude and longitude because I replace lat1, lon1 and lat2, lon2, and I get an error every time.

Where do i put in the values I want for latitude and longitude?

import math

def distance(origin, destination):
    lat1, lon1 = origin
    lat2, lon2 = destination
    radius = 6371 # km

    dlat = math.radians(lat2-lat1)
    dlon = math.radians(lon2-lon1)
    a = math.sin(dlat/2) * math.sin(dlat/2) + math.cos(math.radians(lat1)) \
        * math.cos(math.radians(lat2)) * math.sin(dlon/2) * math.sin(dlon/2)
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1-a))
    d = radius * c

    return d

EDIT: For example, if I have

lat1 = 20 and lon1 = 100 
lat2 = 30 and lon2 = 110

why does it fail when I replace lon1 with the number in the function?

Óscar López · Accepted Answer · 2013-05-30 02:08:32Z

3

Use it like this:

distance((lat1, lon1), (lat2, lon2))

Notice that the function receives as parameters two two-element tuples (or two two-element lists, it'd be the same), each one representing a (latitude, longitude) pair. Equivalently:

origin = (lat1, lon1)
destination = (lat2, lon2)
distance(origin, destination)

answered May 30, 2013 at 2:08

Óscar López

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7 Comments

user2430623 Over a year ago

Im still confused as how to use this as I keep getting error when I try to execute. Say my lat1 = 20 and my lon1 = 100 and lat2 = 30 and lon2 = 110 how would I then put those numbers into your equation and the whole function. Thanks

Óscar López Over a year ago

Like this: distance((20, 100), (30, 200))

user2430623 Over a year ago

Lopez please can you edit the intial code above because Im trying yours and it wont work at all because i keep getting invalid syntax when i type in the tuples as you have shown

Óscar López Over a year ago

It works for me, exactly as I wrote above. You must be doing something else wrong, but my answer is correct, I even tested it with the example, it returns 9818.324994648268.

user2430623 Over a year ago

Thanks all i have it working now it was indeed a whitespace error Oscar :)

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Mariano Anaya · Accepted Answer · 2013-05-30 02:48:44Z

0

You could call it with named parameters by passing tuples for each one, like:

distance(origin=origin_tuple, destination=dest_tuple)

Where

origin_tuple = (origin_lat , origin_long)
dest_tuple = (dest_lat , dest_long)

answered May 30, 2013 at 2:48

Mariano Anaya

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