Python Math libraries - How to?
John Henderson
jhenRemoveThis at talk21.com
Tue Apr 29 04:20:37 CEST 2008
aguirre.adolfo at gmail.com wrote:
> Hi, I am a very newbie who would very much appreciate some
> hints.
>
> Python 2.52. on Windows XP for now. Soon on Ubuntu 8
>
> I am teaching myself Python following free tutorials. I can
> solve problems using arithmetic, but when I try to upgrade the
> programs using math libraries nothing seems to work. I
> downloaded a 2002 tutorial from Zelle "An Introduction to
> Computer Science" where he uses a "import math" statement to
> calculate a square root. I tried the
> "pi" library function but it didn´t work. I tried using def
> Pi() it did not work either. I am yet to find a tutorial that
> explains how to declare (or initialize) and pass numbers to
> the functions such as "cos(x)" and the pi which does not have
> a variable in it. Is just a constant.
>
> Here is the arithmetic program I made that it worked before I
> added
> the "import math" line. I erased the constant p = 3.1416 and
> added the "i" for the library function "pi" in the algorithms.
> But I get an error message not recognizing "pi"
>
>
>
> #volumen.py
> # A program to compute the volume and surface area of a sphere
> import math
Change that line, "import math", to:
from math import *
and it'll work. I'm learning too, so some proficient person
might be able to explain the difference to both of us :)
John
>
> def main():
>
> print "This program calculates the volume and surface area
> of a
> sphere"
> print
> r = input("Please enter the radious: ")
> print
> r3 = r*r*r
> volume = 4/3*pi*r3
> r2 = r*r
> surface = 4*pi*r2
> print "The Volume is", volume, " Cubic centimeters"
> print
> print "The Surface area is", surface, " square
> centimeters"
>
> main()
>
> *** Error message *************
>
> Traceback (most recent call last):
> File "C:/Python25/z - MIS PROGRAMAS/volumen-b.py", line 20,
> in
> <module>
> main()
> File "C:/Python25/z - MIS PROGRAMAS/volumen-b.py", line 13,
> in main
> volume = 4/3*pi*r3
> NameError: global name 'pi' is not defined
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