On 11/21/2010 5:12 AM Chris Begert said...
Hi Gurus
I just wrote my first little python program; so yes I'm very new to all this.
The goal in the end is to have a program that shows how the sun moves from the
point of view of a given location (i.e. solar paths added to some sort of
stereographic diagram).
My very first program calculates the height (altitude) and direction of the sun
(Azimuth) at a specific location during a specific time.
So here's my question (I'm sure its obvious for most of you):
How do I store a years worth of data of angles in an array / list / whatever is
most useful when using Python?
I would look at moving the calculation part into a function that accepts
as input the location, date and time parameters and returns the results.
Then you could write a loop to build the list for the locations and
date ranges of interest. Your choice for data persistence would depend
in part on how the data is to be used and how much there is. Take a
look at the options python comes with at
http://docs.python.org/py3k/library/persistence.html but for small data
sets building the data on the fly may be sufficient as creating a full
year of data at ten minute intervals takes thee seconds on my PC.
Below is how I refactored things.
Emile
-----
import datetime, time
from math import sin
from math import cos
from math import degrees
from math import radians
from math import acos
def getLocation():
print("Please specify your location")
long = float(input("Longitude in degrees: "))
lati = float(input("Latitude in degrees: "))
return long,lati
def getAltAZ (long,lati,month,day,hour,minutes):
time = hour + minutes/60
Nd = datetime.datetime(2010,month,day).timetuple().tm_yday
gdeg = (360/365.25)*(Nd + time/24)
g = radians(gdeg)
D =
0.396372-22.91327*cos(g)+4.02543*sin(g)-0.387205*cos(2*g)+0.051967*sin(2*g)-0.154527*cos(3*g)
+ 0.084798*sin(3*g)
TC =
0.004297+0.107029*cos(g)-1.837877*sin(g)-0.837378*cos(2*g)-2.340475*sin(2*g)
SHA = (time-12)*15 + long + TC
if SHA > 180: SHA = SHA - 360
elif SHA< -180: SHA = SHA + 360
cosSZA =
sin(radians(lati))*sin(radians(D))+cos(radians(lati))*cos(radians(D))*cos(radians(SHA))
SZA = degrees(acos(cosSZA))
altitude = 90 - SZA
cosAZ = (sin(radians(D)) - sin(radians(lati)) * cos(radians(SZA)))
/ (cos(radians(lati))*sin(radians(SZA)))
AZ = degrees(acos(cosAZ))
return altitude,AZ
def prepFullYear(long,lati, interval=10):
return [getAltAZ(long,lati,*time.localtime(t+ii)[1:5]) for ii in
range(0,60*24*365,interval)]
if __name__ == '__main__':
t = time.time()
fy = prepFullYear(100,30)
print (time.time()-t)
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