why no arg, abs methods for comlex type?

[Daniel Schüle]

Hello all,

I often have to deal with complex numbers
using python iteractive as calculator

I wonder why there are no methods like arg, abs

well one can use
c = 1+1j
abs(c)

In my opinion it would also be nice to have the
possibility to write it as
c.abs()
it looks more OO

unfortunately there is no arg method to get the angle
of the complex number
of course it easy to write one on your own
(that's what I have done for myself)
but differnt people will create and reinvite the wheel
over and over again
while reading alien code one will have to spend 2 seconds
remembering the function names etc

consider
c = 1+1j
c.arg(angle_mod e = cmath.GRAD) -> 45.0
or
c.arg(angle_mod e = cmath.RAD) -> 0.7853..

I would also like to see some more functions to make
calculations with complex number more convenient
e.g.
c = 27
c.pow(numerator = 1, denominator = 3,
mode = cmath.EULER, angle_mode = cmath.GRAD)
-> ((3,0), (3,120), (3,240))

what do you think about it?
maybe there exists some proposals aiming this goal?

--
Daniel

[Daniel Schüle]

> I would also like to see some more functions to make

calculations with complex number more convenient
e.g.
c = 27

c = 27+0j

[Terry Reedy]

"Daniel Schüle" <uv**@rz.uni-karlsruhe.de> wrote in message
news:dc******** **@news2.rz.uni-karlsruhe.de...

I wonder why there are no methods like arg, abs well one can use
c = 1+1j
abs(c)

In my opinion it would also be nice to have the
possibility to write it as
c.abs()
it looks more OO
Python is object based but not rigidly OO in syntax or looks. This is an
intentional design decision. Not being gratuitiously redundant is another.
unfortunately there is no arg method to get the angle
of the complex number
I agree that this is a deficiency. I would think .angle() should be a
no-param method like .conjugate(), though its internal implementation would
need access to the appropriate cmath functions. I think returning radians
might be enough though. You could submit to the SourceForge tracker a RFE
(Request For Enhancement) if not a patch.
I would also like to see some more functions to make
calculations with complex number more convenient
e.g.
c = 27
c.pow(numerator = 1, denominator = 3,
mode = cmath.EULER, angle_mode = cmath.GRAD)
-> ((3,0), (3,120), (3,240))
Wanting all roots is fairly specialized. sqrt(4) is 2, not (2, -2).
what do you think about it?
maybe there exists some proposals aiming this goal?

Have you looked for complex math functions in numpy, numarray, scipy or
similar packages? It is possible that a cmath2 module, written in Python,
could be useful.

Terry J. Reedy

[Dan Sommers]

On Fri, 05 Aug 2005 15:42:41 +0200,
Daniel Schüle <uv**@rz.uni-karlsruhe.de> wrote:

Hello all,
I often have to deal with complex numbers
using python iteractive as calculator I wonder why there are no methods like arg, abs well one can use
c = 1+1j
abs(c) In my opinion it would also be nice to have the
possibility to write it as
c.abs()
it looks more OO
I guess it's for the same reason that we are spared
from writing things like this:

z = x.squared().add ed_to(y.squared ()).squareroot( )
E = m.multiplied_by (c.squared())

More OO, yes. More readable, not IMO.
I would also like to see some more functions to make
calculations with complex number more convenient
[ ... ]
maybe there exists some proposals aiming this goal?

SciPy or Numeric?

Regards,
Dan

--
Dan Sommers
<http://www.tombstoneze ro.net/dan/>

[Dan Bishop]

Terry Reedy wrote:

"Daniel Schüle" <uv**@rz.uni-karlsruhe.de> wrote in message
news:dc******** **@news2.rz.uni-karlsruhe.de...

....

unfortunately there is no arg method to get the angle
of the complex number

I agree that this is a deficiency. I would think .angle() should be a
no-param method like .conjugate(), though its internal implementation would
need access to the appropriate cmath functions.

You need math, not cmath.

def arg(z):
"""The Argument of z, in radians."""
z += 0j # make it work on real inputs
return math.atan2(z.im ag, z.real)

[Dennis Lee Bieber]

On Fri, 05 Aug 2005 15:42:41 +0200, Daniel Schüle
<uv**@rz.uni-karlsruhe.de> declaimed the following in comp.lang.pytho n:

c = 1+1j
c.arg(angle_mod e = cmath.GRAD) -> 45.0
Is that right? The result looks more like Degrees...

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=============== =============== =============== =============== == <
Home Page: <http://www.dm.net/~wulfraed/> <
Overflow Page: <http://wlfraed.home.ne tcom.com/> <

[Daniel Schüle]

Hi Terry,

In my opinion it would also be nice to have the
possibility to write it as
c.abs()
it looks more OO

Python is object based but not rigidly OO in syntax or looks. This

is an intentional design decision. Not being gratuitiously redundant is another.

I agree, redundancy confuses people

unfortunate ly there is no arg method to get the angle
of the complex number

I agree that this is a deficiency. I would think .angle() should be a
no-param method like .conjugate(), though its internal implementation

would need access to the appropriate cmath functions. I think returning radians might be enough though.
I don't know what nomenclature is used in english speaking
mathematical world for angle of a complex number
I learned it in german as Arg(z) .. Arg standing for argument
you see, we would have named it differently, hence making
it difficult for the reader, eventually creating redundancy
You could submit to the SourceForge tracker a RFE
(Request For Enhancement) if not a patch.
I never did, but I will see

c = 1 + 1j
def arg(c, angle_mode = "RAD"): .... if angle_mode not in ("RAD", "GRAD"):
.... raise ValueError
.... import math
.... ret = math.atan2(c.im ag, c.real)
.... if angle_mode == "GRAD":
.... return ret / math.pi * 180
.... return ret

it's pretty easy and straightforward implementation
while writing this, I was struck by an idea and
reimplemented it as following
def arg(self, angle_mode = "RAD"): .... if angle_mode not in ("RAD", "GRAD"):
.... raise ValueError
.... import math
.... ret = math.atan2(self .imag, self.real)
.... if angle_mode == "GRAD":
.... return ret / math.pi * 180
.... return ret
.... class Complex(complex ): pass
Complex.arg = arg
c = Complex(1+1j)
c.arg(angle_mod e = "GRAD")

45.0

later I realized that this represents "yet another implementation"
which could be done by someone, thus again leading to possible
redundancy and confuse people

all this would not have happened when we would have
arg or angle builtin in complex type

I would also like to see some more functions to make
calculation s with complex number more convenient
e.g.
c = 27
c.pow(numerat or = 1, denominator = 3,
mode = cmath.EULER, angle_mode = cmath.GRAD)
-> ((3,0), (3,120), (3,240))

Wanting all roots is fairly specialized. sqrt(4) is 2, not (2, -2).

it could be named .allroots(n) -> ((), (), ())
with n whole number

indeed .pow() is not a good name for it, since z**x
always yields one complex number

if x is 2.5 or alike, it could be aproximated with n/m and use
res = []
for i in z.allroots(m):
res.append(i**n )

I am not sure, this is correct iterpretation of z**2.5
I will need to ask in math newsgroup :)
and approximation might not be good enough
Have you looked for complex math functions in numpy, numarray, scipy or
similar packages? It is possible that a cmath2 module, written in Python, could be useful.

I hope so
I will google for cmath2, I never heard about it
I am new to Numeric and numarray, I was playing with them and
ufunc-tionsand matplotlab, as for SciPy I couldnt find
any binary for 2.4 Python unfortunately :-/

Regards

--
Daniel

[Daniel Schüle]

>>c = 1+1j

c.arg(angle_m ode = cmath.GRAD) -> 45.0

Is that right? The result looks more like Degrees...

maybe I confuse, in german one would say "45 Grad"
I took a freedom to translate it directly :)
well, my calculator shows a "D"
which most likely stands for Degree, I cannot tell for sure

--
Daniel

[Erik Max Francis]

Daniel Schüle wrote:

what do you think about it?
maybe there exists some proposals aiming this goal?

Derive your own subclass of complex and define those methods.

--
Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
I am not afraid / To be a lone Bohemian
-- Lamya

[Erik Max Francis]

Daniel Schüle wrote:

maybe I confuse, in german one would say "45 Grad"
I took a freedom to translate it directly :)
well, my calculator shows a "D"
which most likely stands for Degree, I cannot tell for sure

Probably. In English, you have degrees and gradians, which aren't the
same thing; gradians are defined so that there are 400 gradians in a
circle (so 100 gradians in a right angle).

--
Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
I am not afraid / To be a lone Bohemian
-- Lamya