[Numpy-discussion] cos -- NameError: global name 'cos' is not defined

Wayne Watson sierra_mtnview@sbcglobal....
Mon Dec 21 13:44:44 CST 2009


Yes, one can get both sin and cos via the interactive shell, if math is 
imported as you have done.
However, I thought math itself always present to a program module?  In 
my program, sin exists but not cos, so one is forced to use math.cos(). 
Why one but not the other?


Keith Goodman wrote:
> On Mon, Dec 21, 2009 at 9:40 AM, Wayne Watson
> <sierra_mtnview@sbcglobal.net> wrote:
>   
>> In this code,
>> ===========start
>> import math
>> import numpy as np
>> from numpy import matrix
>> def sinD(D): # given in degrees, convert to radians
>>    return sin(radians(D))
>> def cosD(D):
>>    return cos(radians(D))   <<--------------
>> def acosD(D):
>>    acos(radians(D))
>>    return=====end
>> the << line produces, "NameError: global name 'cos' is not defined", but
>> the sin() above it does not? They are both built-in functions.
>>     
>
>   
>>> sin(10)
>>>       
> NameError: name 'sin' is not defined
>
> Oh, right, there is no built-in sin function. I need to import it:
>
>   
>>> import numpy as np
>>> import math
>>>
>>> math.sin(1)
>>>       
>    0.8414709848078965
>   
>>> np.sin(1)
>>>       
>    0.8414709848078965
>
> or
>
>   
>>> from numpy import sin
>>> sin(1)
>>>       
>    0.8414709848078965
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>   

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           Wayne Watson (Watson Adventures, Prop., Nevada City, CA)

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