CODEWITHSUNDEEP
pythonlambdasyntax-errorpython-3.6
Insendio FX
Insendio FX

Reputation: 61

How to make this lambda work correctly in Python3?

Why does this code:

import math

def nearest_location(locations, my_location):
    return min(enumerate(locations), key=lambda (_, (x, y)): math.hypot(x - my_location[0], y - my_location[1]))

locations = [(41.56569, 60.60677), (41.561865, 60.602895), (41.566474, 60.605544), (41.55561, 60.63101), (41.564171, 60.604020)]
my_location = (41.565550, 60.607537)

print(nearest_location(locations, my_location))

throw errors like:

Tuple parameter unpacking is not supported in python 3

and

SyntaxError: invalid syntax

When i run it on Python 3.6?

I tried to fix it myself, but I still do not get it... Can somebody help to fix it?

Upvotes: 2

Views: 262

Answers (1)

MSeifert
MSeifert

Reputation: 152667

You can't unpack the arguments for lambda in python-3.x. While they can still accept multiple arguments (i.e. lambda x, y: x+y) you can't unpack one argument anymore (i.e. lambda (x, y): x+y).

The simplest solution would be to just index the "one argument" instead of using unpacking:

import math

def nearest_location(locations, my_location):
    return min(enumerate(locations), key=lambda x: math.hypot(x[1][0] - my_location[0], x[1][1] - my_location[1]))

locations = [(41.56569, 60.60677), (41.561865, 60.602895), (41.566474, 60.605544), (41.55561, 60.63101), (41.564171, 60.604020)]
my_location = (41.565550, 60.607537)

print(nearest_location(locations, my_location))
# (0, (41.56569, 60.60677))

Upvotes: 1

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