Comparing a float and an int in Python

Question

I am trying to see if the calculated distance between two points is smaller than a given radius like this:

if distance(lat1, long1, lat2, long2) < radius:         


        

Answer 1

Just compare them directly, there is no harm in that at all.

Python handles comparing numbers of different types perfectly well:

>>> type(1.1)
<class 'float'>
>>> type(1)
<class 'int'>
>>> 1.1 > 1
True
>>> 1.1 < 1
False
>>> 1 < 2
True
>>> 2.2 == 2.2
True
>>> 2 == 2.2
False
>>> 1.6 < 2
True
>>> 1.6 > 2
False
>>> 1.6 == 2
False

Python is duck typed, so in general you shouldn't worry about types directly, just if they can work in the way you need.

There could be some issues with comparing floats for equality with other floats due to precision errors:

>>> 0.3+0.3+0.3 == 0.9
False
>>> 0.3+0.3+0.3
0.8999999999999999

But in comparing to ints and/or < or > operations, you shouldn't worry.

In your update, we can use the decimal module to show the cause:

>>> Decimal(1.2000000000000001)
Decimal('1.20000000000000017763568394002504646778106689453125')
>>> Decimal(1.20000000000000001)
Decimal('1.1999999999999999555910790149937383830547332763671875')

But does this really matter? It's an inherent problem with floating point numbers, but only matters where you need really high precision.