This issue is probably older than I am, and was amazed to discover it in
python:
Python 2.5.2 (r252:60911, May  7 2008, 15:19:09)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
>>> int(float("-23.15"))
-23
>>> int(float("-23.65"))
-23
>>> int(float("24.9"))
24
>>> int(float("24.4"))
24
Is this by design? What is the python way of obtaining a correct result?

I don't see any problem with that result? Why do you consider the result
incorrect, and what "correct" result would you have inspected instead?

Notice that int conversion of floats truncates them, by definition.

Hello,
As far as I know, the correct conversion is to either round to the
nearest, or to the smaller integer, but not both.

Sorry for not writing completely above - python does neither, it rounds
to the integer closest to zero

I see. There is no such thing as a "correct" conversion from real
numbers to integer numbers. Instead, there are various approaches,
called "truncating", "rounding", "flooring", and "ceiling". Python's
default conversion is truncation, and it is consistent in doing so:
int(x) will return the nearest integer between 0 and x.

If you want rounding, use the round builtin.

This is exactly what int() is supposed to do.  For other kinds of 
rounding, look at round(), math.floor(), math.ceil(), and many rounding 
options in the decimal module:

from decimal import Decimal
>>> Decimal('-23.15').to_integral(ROUND_FLOOR)
Decimal("-24")
>>> Decimal('-23.15').to_integral(ROUND_CEILING)
Decimal("-23")
>>> Decimal('-23.15').to_integral(ROUND_DOWN)
Decimal("-23")
>>> Decimal('-23.15').to_integral(ROUND_HALF_EVEN)
Decimal("-23")