Question

How can I write Q array to excel after the loop ends? Or How can I see the data that is stored in Q after the loop ends?

Nlayers=23
N=365

def main_loop(Z,z,Areat0,Areat1,TempLake,i,HSR,TD,FW,wind):
    Q=np.zeros(len(rad))
    Q[0]=0
    Q[i+1]=Qn(HSR,TD,FW,TempLake[0])
    Q0=Q[i]
    Q1=Q[i+1]
    n=TempLake.size
    var00=Imp_scheme(Q0,Q1,z,Areat0,Areat1,Z,TempLake,wind)
    var01=fix_profile(n,var00,Areat0)
    return var01

TempLake=np.zeros((N,Nlayers))
TempLake[0]=T0

for i in xrange(N-1):
    TempLake[i+1]=main_loop(Z,z,Areat0,Areat1,TempLake[i],i,HSR[i],TD[i],FW[i],wind[i]) 

Answer 1

The short answer is that you can’t without a) returning it, b) passing it in and modifying it, or c) declaring it as a global or something equivalent. In most cases a is the best. In the last line of the function, you could do this:

return var01, Q

And in the main for loop:

for i in xrange(N-1):
    result, Q = main_loop(...)
    TempLake[i + 1] = result
do_something_with(Q)

But this is a rather awkward design in your case, since you’re returning Q N times, but only using it once. Probably there’s a better approach, but I can’t tell from your example code what you’re really doing, so I can’t figure out what it might be.