[Tutor] Use of sqrt() from math module
زياد بن عبدالعزيز البات
زياد بن عبدالعزيز البات
Sat Dec 1 16:04:15 CET 2007
Matt Smith wrote:
> Hi,
Hi...
>
> I need to find the square root of a number in a program I am writing. I have
> imported the 'math' module so I thought I could just call sqrt(x) but I get an
> error message. Extact from my code and error message below.
>
>
> import sys, pygame, math
You import the module "math", not what's _inside_ it! (This is
important! Both ways are okay, but in your case this is important!)
>
> ...
>
> if ypos >= 384 and velocity > 0:
> impactvel = sqrt(velocity ** 2 + (2 * gravity * (ypos - 384 * 160)))
>
> ...
Where did you get this thing called "sqrt"? You didn't define a
function called "sqrt", did you?
What you need is the "sqrt" function (or method) that lives _inside_ the
"math" module, and you *must* tell that to Python, otherwise it won't
find it!
To fix your problem, either:
- Use: "from math import sqrt". But this will import the "sqrt"
function only. If all you need from the "math" module is this
function/method then this is fine. (Though, this is generally not
good practice, since you'll pollute you name space. The other
solution is better.)
- Or in the line that triggers the error, use: "math.sqrt(..." instead.
By using "math." you tell Python where to find this thing that's
called "sqrt", which is what you want.
>
>
> Traceback (most recent call last):
> File "<stdin>", line 32, in <module>
> ValueError: math domain error
I see you sent a new message with the actual error which is:
Traceback (most recent call last):
File "<stdin>", line 32, in <module>
ValueError: math domain error
which confirm what I wrote above.
Hope this helps.
Ziyad.
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