X root Operator help

[lucidparadox]

I'm currently new to Python and I haven't been able to find the
operator/math function to find the square root or even the x root of a
number. I'm rewriting a program that I wrote in BASIC that does the
math of a quadratic equation (user puts in a, b, and c values) and
tells the user whether it has 1 root, 2 roots, or no real roots and
displays the roots if it has real roots.

Thanks in advance,
Dan

[Tim Golden]

lucidparadox wrote:

I'm currently new to Python and I haven't been able to find the
operator/math function to find the square root or even the x root of a
number.

Without ever having used it, I would guess
it's the sqrt function in the math module.

(Possibly also of interest: the pow function
in that same module)
TJG

[Michael Hoffman]

lucidparadox wrote:

I'm currently new to Python and I haven't been able to find the
operator/math function to find the square root or even the x root of a
number.

For square root, use math.sqrt(y)

For x root use y**(1/x)

I'm rewriting a program that I wrote in BASIC that does the
math of a quadratic equation (user puts in a, b, and c values) and
tells the user whether it has 1 root, 2 roots, or no real roots and
displays the roots if it has real roots.

In floating point arithmetic, the naive way of calculating both roots
always using the formula (-b +/- sqrt(b**2 - 4*a*c))/2*a will give you
inaccurate results sometimes. See
<http://www.cse.uiuc.edu/eot/modules/floating_point/quadratic_formula/>.

For a better formula, see how r_1 and r_2 are defined in
<http://en.wikipedia.org/wiki/Quadratic_equation#Alternative_formula>.
--
Michael Hoffman

[lucidparadox]

On Apr 18, 8:52 am, Michael Hoffman <[e-mail]:

lucidparadox wrote:

I'm currently new to Python and I haven't been able to find the
operator/math function to find the square root or even the x root of a
number.

For square root, use math.sqrt(y)

For x root use y**(1/x)

I'm rewriting a program that I wrote in BASIC that does the
math of a quadratic equation (user puts in a, b, and c values) and
tells the user whether it has 1 root, 2 roots, or no real roots and
displays the roots if it has real roots.

In floating point arithmetic, the naive way of calculating both roots
always using the formula (-b +/- sqrt(b**2 - 4*a*c))/2*a will give you
inaccurate results sometimes. See
<http://www.cse.uiuc.edu/eot/modules/floating_point/quadratic_formula/>.

For a better formula, see how r_1 and r_2 are defined in
<http://en.wikipedia.org/wiki/Quadratic_equation#Alternative_formula>.
--
Michael Hoffman

Thanks. As of right now I'm just trying to familiarize myself with
the syntax of Python. Actually I should have thought of y**(1/x).
I'm currently a freshman in college so the alternative formula hasn't
been introduced to me yet. Thanks for the pointers though.

Dan Collins

[Michael Hoffman]

[Michael Hoffman]

>In floating point arithmetic, the naive way of calculating both roots
always using the formula (-b +/- sqrt(b**2 - 4*a*c))/2*a will give you
inaccurate results sometimes. See
<http://www.cse.uiuc.edu/eot/modules/floating_point/quadratic_formula/>.

[lucidparadox]

Thanks. As of right now I'm just trying to familiarize myself with
the syntax of Python. Actually I should have thought of y**(1/x).

math.sqrt(y) might be faster or even more accurate (depending on
platform) than y**0.5.

I'm currently a freshman in college so the alternative formula hasn't
been introduced to me yet.

It probably won't be unless you take a class in numerical analysis. Many
a person has been burned by not thinking about these sorts of things
until it is too late (myself included).
--
Michael Hoffman

[Steve Holden]

Michael Hoffman wrote:

lucidparadox wrote:

>I'm currently new to Python and I haven't been able to find the
operator/math function to find the square root or even the x root of a
number.

For square root, use math.sqrt(y)

For x root use y**(1/x)

[...]

>>1/3

0

>>3.14159 ** (1/3)

1.0

>>>

So the cube root of pi is 1? I don't think so.

For generic roots use y ** (1.0 / x)

until future versions of Python produce floating point results from all
divisions as necessary.

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden
Recent Ramblings http://holdenweb.blogspot.com

[Michael Hoffman]

[Michael Hoffman]

>For x root use y**(1/x)

[Steve Holden]

>>3.14159 ** (1/3)

1.0

>>>

So the cube root of pi is 1? I don't think so.

For generic roots use y ** (1.0 / x)

Yes, good point. :)
--
Michael Hoffman

[jim-on-linux]

python help,

A client is using win xp home.

my program contains;
shutil.copyfile(n, 'prn')

This runs fine on win xp pro but they are getting
the following traceback.

File "LOP_PRT_10.pyc", line 170, in __init__
* File "LOP_PRT_10.pyc", line 188, in Fprint1
* File "shutil.pyc", line 47, in copyfile
IOError: [Errno 2] No such file or directory:
'prn'

Since this runs ok on win xp pro, does this have
something to do with the home version of xp.

I'm thinking of changeing 'prn' to 'lpt1' and
trying again but I don't want to use the client
as a testor. Or is there some other explaination
for the problem.

jim-on-linux

[Tim Golden]

jim-on-linux wrote:

python help,

A client is using win xp home.

my program contains;
shutil.copyfile(n, 'prn')

This runs fine on win xp pro but they are getting
the following traceback.

File "LOP_PRT_10.pyc", line 170, in __init__
File "LOP_PRT_10.pyc", line 188, in Fprint1
File "shutil.pyc", line 47, in copyfile
IOError: [Errno 2] No such file or directory:
'prn'

Since this runs ok on win xp pro, does this have
something to do with the home version of xp.

I'm thinking of changeing 'prn' to 'lpt1' and
trying again but I don't want to use the client
as a testor. Or is there some other explaination
for the problem.

Not that this is your question, but if you're
trying to print under Windows have you looked
at:

http://tgolden.sc.sabren.com/python/...o_i/print.html

for alternatives?

TJG

[jim-on-linux]

On Wednesday 18 April 2007 17:02, Tim Golden
wrote:

jim-on-linux wrote:

python help,

A client is using win xp home.

my program contains;
shutil.copyfile(n, 'prn')

This runs fine on win xp pro but they are
getting the following traceback.

File "LOP_PRT_10.pyc", line 170, in __init__
File "LOP_PRT_10.pyc", line 188, in Fprint1
File "shutil.pyc", line 47, in copyfile
IOError: [Errno 2] No such file or directory:
'prn'

Since this runs ok on win xp pro, does this
have something to do with the home version of
xp.

I'm thinking of changeing 'prn' to 'lpt1'
and trying again but I don't want to use the
client as a testor. Or is there some other
explaination for the problem.

Not that this is your question, but if you're
trying to print under Windows have you looked
at:
http://tgolden.sc.sabren.com/python/win32_how_d
o_i/print.html

for alternatives?

TJG

Thanks for the response,

I got the following to work on windows.

win32api.ShellExecute (
0, 'print',
filename, None, ".", 0
)

However it prints the name of the file at the top
and adds a page number on the bottom. Is there
some way of eliminating the filename and page
number.
jim-on-linux

[Tim Golden]

jim-on-linux wrote:

On Wednesday 18 April 2007 17:02, Tim Golden
wrote:

>jim-on-linux wrote:

>>python help,

A client is using win xp home.

my program contains;
shutil.copyfile(n, 'prn')

This runs fine on win xp pro but they are
getting the following traceback.

File "LOP_PRT_10.pyc", line 170, in __init__
File "LOP_PRT_10.pyc", line 188, in Fprint1
File "shutil.pyc", line 47, in copyfile
IOError: [Errno 2] No such file or directory:
'prn'

Since this runs ok on win xp pro, does this
have something to do with the home version of
xp.

I'm thinking of changeing 'prn' to 'lpt1'
and trying again but I don't want to use the
client as a testor. Or is there some other
explaination for the problem.

Not that this is your question, but if you're
trying to print under Windows have you looked
at:
http://tgolden.sc.sabren.com/python/win32_how_d
o_i/print.html

for alternatives?

TJG

Thanks for the response,

I got the following to work on windows.

win32api.ShellExecute (
0, 'print',
filename, None, ".", 0
)

However it prints the name of the file at the top
and adds a page number on the bottom. Is there
some way of eliminating the filename and page
number.

Unfortunately, this approach is quick-and-dirty and
you're at the mercy of whatever the "print" verb
does to "filename" on your box. (Although you
can configure that if you try hard enough).

I'm afraid if you want control, you'll have to
go the PDF route or to automate Word / OpenOffice
etc.

TJG

[jim-on-linux]

Thanks Tim for resopnding,
I appreciate the help.

I convinced the client to install Linux on 4
machines rather than upgrade from xp home to XP
Pro, and more machines to come if the like it.

jim-on-linux
On Friday 20 April 2007 03:22, you wrote:

jim-on-linux wrote:

On Wednesday 18 April 2007 17:02, Tim Golden

wrote:

jim-on-linux wrote:
python help,

A client is using win xp home.

my program contains;
shutil.copyfile(n, 'prn')

This runs fine on win xp pro but they are
getting the following traceback.

File "LOP_PRT_10.pyc", line 170, in
__init__ File "LOP_PRT_10.pyc", line 188,
in Fprint1 File "shutil.pyc", line 47, in
copyfile IOError: [Errno 2] No such file or
directory: 'prn'

Since this runs ok on win xp pro, does this
have something to do with the home version
of xp.

I'm thinking of changeing 'prn' to 'lpt1'
and trying again but I don't want to use
the client as a testor. Or is there some
other explaination for the problem.

Not that this is your question, but if
you're trying to print under Windows have
you looked at:
http://tgolden.sc.sabren.com/python/win32_ho
w_d o_i/print.html

for alternatives?

TJG

Thanks for the response,

I got the following to work on windows.

win32api.ShellExecute (
0, 'print',
filename, None, ".", 0
)

However it prints the name of the file at the
top and adds a page number on the bottom. Is
there some way of eliminating the filename
and page number.

Unfortunately, this approach is quick-and-dirty
and you're at the mercy of whatever the "print"
verb does to "filename" on your box. (Although
you can configure that if you try hard enough).

I'm afraid if you want control, you'll have to
go the PDF route or to automate Word /
OpenOffice etc.

TJG