Is there a prefab python function out there that turns only integer floats into ints?-CodePudding

I would like to turn float integers (123.0) into ints (123).

What I would like the function to do:

Input: 2.1 Output: Exception, cannot turn float into int

Input: 2.0 Output: 2

Using int() on a float seems to just be math.floor() and that is not what I'm looking for.

CodePudding user response：

You can check if after you use int() it the same value as the float

def convert(num):
    if num == int(num):
        return int(num)
    raise Exception('Cannot turn float into int')

As a side note, using int() is not exactly as using math.floor(), try with negative numbers. What is the difference between int() and floor() in Python 3?

CodePudding user response：

I guess i would just do

def convert(n):
    return int(f"{n:g}")

CodePudding user response：

I don't know of a build in that does it directly, but it is easy to create your own function. You can use .is_integer() on the input-value to check if the float is directly castable to int:

def strict_int(value):
    if value.is_integer():
        return int(value)
    raise ValueError("cannot turn uneven float into int")


print(strict_int(3.0))
print(strict_int(3.1))

Output:

3
...
ValueError: cannot turn uneven float into int

But be warned, that there may be some unexpected behavior resulting from the way floats are represented. Try this for example:

print(strict_int(0.3   0.3   0.3   0.1))

This "1.0" will not be able to directly cast to int as it is in fact 0.9999999999999999! But this is a general issue with how floats are represented and not directly related to the used functions. So you'll encounter this with any method.

Here is an interesting post that goes a bit more into detail about the potential issues.