On 14 June 2011 15:20, amt <0101...@gmail.com> wrote: >>> But I can't understand at line 2 and 3. I mean it makes no difference >>> for me. Saying 30 or 30.0 is the same thing. >>> As well as saying 97 or 97.0. >> >> Precisely, thats why I asked the question. > > As a beginner at line 2 and 3 I see no point of using floating numbers > except the fact to serve as an example that if I have a floating point > number it affects the rest of the expression evaluation.
Correct, 2 and 3 do not need floating point arithmetic. > So, should I keep them or not?It's unclear to me and sadly the author of the > book doesn't provide the solutions to the exercises. The only way I can > verify myself is using this list. If you tell Python to divide 2 integers (whole numbers) by default it will use integer arithmetic. So in your calculation on line 5 you get a result of 7 as Python does not switch to floating point arithmetic. You can ask Python to use floating point arithmetic a couple of ways. For example if you want 2 divided by 3 you can tell Python to use floating point arithmetic by: --1-- >>> float(2) / 3 0.6666666666666666 >>> float(20) / 7 2.857142857142857 --2-- >>> 2.0 / 3 0.6666666666666666 >>> 20.0 / 7 2.857142857142857 What happens here is that Python on one side of the division has a floating point number. This will force it to use floating point arithmetic instead of integer. Generally the second form is used and the first is for demonstration purpose only. >>> 2 / 3 0 >>> 20 / 7 2 Here we have 2 integers and therefor Python uses integer arithmetic and gives 0 and 2 as result. This is because the results of the division can not be stored as an integer so everything after the decimal place gets cut off. In Python 3 this has been changed that by default it will do floating point arithmetic. You can also get this in Python 2 by importing division from __future__. The Python tutorial [1] on floating point arithmetic will give you much more info on floating point arithmatic in Python. Greets Sander [1] http://docs.python.org/tutorial/floatingpoint.html _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor