from pylab import *
def Jahresgang(t,S,Em,Eb):
    E = (Em-Eb)/2*(1+sin((2*3.14)*t/365-S))+Eb
    return E
t = arange(1.0, 365.0, 7.0)
plot(t, Jahresgang(t,90,5.0,0.5))
ytext = ylabel('Verdunstung (mm)')
xtext = xlabel('Zeit (Tag)')
show()