Re: Problem calling math.cos()

Sambo <sambo@xxxxxxxx> wrote:

I have the following module:
-------------------------------
import math

def ac_add_a_ph( amp1, ph1, amp2, ph2 ):

amp3 = 0.0
ph3 = 0.0
ac1 = ( 0, 0j )
ac2 = ( 0, 0j )
ac3 = ( 0, 0j )

You're defining ac1, ac2, ac3 as tuples, each with two items. That's
silly: remove these three useless and confusing lines (the first two are
prety silly too). No damage, but, avoidable extra confusion.

ac1 = complex( amp1 * math.cos( math.radians( ph1 ) ), amp1 * \
math.sin( math.radians( ph1 ) ) )
ac2 = complex( amp2 * math.cos( math.radians( ph2 ) ), amp2 * \
math.sin( math.radians( ph2 ) ) )
ac3 = ac1 + ac2
amp3 = math.abs( ac3 )
ph3 = math.atan( ac3.imag / ac3.real )
return [amp3, ph3]
--------------------------------------
when I import it (electronics) in python.exe in windows2000 and
try to use it, it croaks. ???

import math
import electronics
print electronics.ac_add_a_ph( 10, 0 , 6 , 45 )
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "f:\devel\python\electronics.py", line 10, in ac_add_a_ph
ac1 = complex( amp1 * math.cos( math.radians( ph1 ) ), amp1 * \
math.sin( math
.radians( ph1 ) ) )

[[some lines split to respect NNTP's constraint on 80-char lines]]

NameError: global name 'cos' is not defined



global?? huh?

Weird -- I can't reproduce this; it's the kind of symptom you get when
mistakenly using a comma instead of a dot, for example, but I don't see
that error in your code.

What I _do_ see is an "AttributeError: 'module' object has no attribute
'abs'" on the amp3 assignment -- of course, because that's indeed the
fact (abs is a builtin, not a member to module math).

Most likely, you got a bit confused and didn't copy-and-paste exactly
what was going on.


what does abs stand for? why is that not absolute value? hmmm.

abs does stand for absolute-value.

Hmm, complex numbers, cool I don't even have any idea where C
stands on this.

C has no stand on complex numbers.


Alex
.

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