Problem related to the use of int() in a script

Python Help
1

hello,
I am trying to write a Python script that converts a list of numbers containing integers and floating point numbers into a list of integers. I used the Geany editor for the script and the Idle shell to test it:

numbers = input(“enter a list of numbers separated by commas: “)
list = numbers.split(”,”)
list_integers = []
for numbers in list:
integers = int(numbers)
list_integers.append(integers)
print(list_integers)

If I enter the numbers [1, 6.3]I get this error :

Traceback (most recent call last):
File “<pyshell#91>”, line 2, in
integers = int(numbers)
ValueError: invalid literal for int() with base 10: ’ 6.3’

If I replace 6.3 with 6, everything works correctly. Why does the int() function not accept a floating point number in this specific case?

PS: I am just starting to learn the Python language.

2

int()can operate in two ways.

If you pass in a floating point number, it will truncate the number and return an integer value.

If you pass in a string[1]that represents an integer, it will convert the string to a number and return that integer.

It does not take a string that represents a floating point number and do both steps of converting from the string and truncation. If you want to do that, you might instead do int(float(x)).

  1. String, byte, or bytearray ↩︎

2 Likes
3

I tried your solution and it worked well. Now I need to understand it and find out a little more about what exactly int() does.

Anyway, thank you very much.

4

Have a look here in the official python documentation: Built-in Functions — Python 3.13.7 documentation

And here for all builtin functions: Built-in Functions — Python 3.13.7 documentation

5

Using link #2, I think I’ve found the explanation for my mistake:
1- I thought the int() argument was a number: 6.3. In reality, it was a string: “6.3”.
2- In the documentation Built-in Functions — Python 3.13.7 documentation I found this line:
If the argument is not a number or if base is given, then it must be a string, bytes, or bytearray instance representing an integer in radix base.
So int(“6.3”) cannot be interpreted because the decimal point has no associated value and cannot be represented by a number. This must be the reason for “It does not accept a string that represents a floating point number.”
That is how I interpret my error.

6

Exactly. int either takes any number and turns it into an integer.

>>> int(123.45)
123

Or, it takes a string that represents an integer and turns that into an actual integer.
And it allows some whitespace in there.

>>> int('   -12_345\n')
-12345

But it does NOT allow you to pass a string that represents any number

>>> int("123.45")
ValueError: invalid literal for int() with base 10: '123.45'

So if you have a string that represents a floating point number, you first need to convert it into a floating point number

>>> my_string = "123.45"
>>> my_float = float(my_string)
>>> my_float
123.45
>>> my_int = int(my_float)
>>> my_int
123

Or short int(float(my_string)

If you use the string version you can also specify the base of the number, the docs have this nice block to show this

>>> int(123.45)
123
>>> int('123')
123
>>> int('   -12_345\n')
-12345
>>> int('FACE', 16)
64206
>>> int('0xface', 0)
64206
>>> int('01110011', base=2)
115