what is this?

[Herbert Fritsch]

Hi,
I'm a real beginner with python and I don't really know if I will get it.
But here is one of my first exercises:

Python 2.3+ (#1, Sep 23 2003, 23:07:16)
[GCC 3.3.1 (SuSE Linux)] on linux2
Type "help", "copyright", "credits" or "license" for more information.0.80000000000000004

There must be something wrong. I' running the new Suse 9.0.

Herbert

 

[Peter Otten]

0.80000000000000004

There must be something wrong. I' running the new Suse 9.0.

No

That's the way *all* floating point operations work, nothing python-specific
here. See

http://www.python.org/doc/faq/general.html#why-are-floating-point-calculations-so-inaccurate

Peter

 

[Jay Dorsey]

0.80000000000000004

There must be something wrong. I' running the new Suse 9.0.

Not really. Think of the order of operations in mathematics.
Multiplication and division are ranked higher than addition. Using
parentheses for grouping is higher (before) mulitplication and division.

First example:

4 / 2 + 3 yields 2 + 3 yields 5

Second:

4 / (2.0 + 3)

Python coerces the 3 into a floating point number, so lets write all
these as floating points:

4.0 / (2.0 + 3.0)

Order of operations says do the parentheses first:

4.0 / 5.0 yields 0.8000000000000004

Theres a listing of Pythons order of operations somewhere in the
documentation on python.org (couldn't find it with a quick search).

 

[Hari Pulapaka]

Hi,

Most newbies to python, have probably experienced this one time or
another. And posted it to the newsgroups, where the Python gurus, will
say, No foo thats how floating points are represented, read the tutorial
and understand floating point representation, etc...

But call it whatever, 3.4 != 3.3999999999999999 and I feel that
somewhere some change should be made so that the representation is better.

I saw some discussion earlier where, someone provided a function for
repr so that the presentation of floating is better and it looked like
(to me) that it had a solution for this problem.

- Hari

Hi,
I'm a real beginner with python and I don't really know if I will get it.
But here is one of my first exercises:

Python 2.3+ (#1, Sep 23 2003, 23:07:16)
[GCC 3.3.1 (SuSE Linux)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

5

0.80000000000000004

There must be something wrong. I' running the new Suse 9.0.

Herbert