Appending a temp file in a for loop - loops

Question

I have three arrays of data. I want to loop them over and save the values in a temporary file if some condition is meet. If the condition is not meet I would like to open the temorary file and find the index of the maximum value then save to another file. When I try the code below I get this error. This is my fist time using tempfile.NamedTemporaryFile() so I very well may not be using it correctly. Thanks
Traceback (most recent call last):
File "<ipython-input-19-7c44ca7dcbd6>", line 1, in <module>
runfile('C:/Users/Khary/Documents/Astrophysics/Bolshoi/Halo Formation History Project/Codes/Find V_max.py', wdir='C:/Users/Khary/Documents/Astrophysics/Bolshoi/Halo Formation History Project/Codes')
File "C:\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 685, in runfile
execfile(filename, namespace)
File "C:\Anaconda3\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 85, in execfile
exec(compile(open(filename, 'rb').read(), filename, 'exec'), namespace)
File "C:/Users/Khary/Documents/Astrophysics/Bolshoi/Halo Formation History Project/Codes/Find V_max.py", line 222, in <module>
formation_def()
File "C:/Users/Khary/Documents/Astrophysics/Bolshoi/Halo Formation History Project/Codes/Find V_max.py", line 129, in formation_def
FT = np.loadtxt(TF,skiprows=0)
File "C:\Anaconda3\lib\site-packages\numpy\lib\npyio.py", line 770, in loadtxt
first_line = next(fh)
UnsupportedOperation: not readable
My code
import numpy as np
import temp
#large arrays of data
Id = np.array([some size])
MASS = np.array([some size])
V = np.array([some size])
def filesave(MAS,V): #Functioin to write and save values to file
Mc = str(MAS)
Vel = str(V)
w.write(Mc)
w.write('\t')
w.write(Vel)
w.write('\n')
return()
def formation_def():
count = 1
l =len(ID)
for i in range(l):
if ID[i] == count:
for j in range(i,l):
TF = tempfile.NamedTemporaryFile(mode='a')
if ID[j] <= ID[i]:
T = str(ID[j])
M = str(MASS[j])
Vel = str(V[j])
TF.write(T)
TF.write('\t')
TF.write(M)
TF.write('\t')
TF.write(Vel)
TF.write('\n')
elif ID[j]>ID[i]: # if ID[j]>TID[i] then we are in the next halo in the list
FT = np.loadtxt(TF,skiprows=0)
MASS2 = FT[:,0]
V2 = FT[:,2]
vel_max = np.argmax(V2)
filesave(MASS2[vel_max],V2[vel_max])
TF.close()
count+=1 # and must indcrement the counter and break out of loop
break
elif:
count = ID[i]+1
return()

Answer 1

When you created your temporary file, you assigned it to append data to the file. That is a write operation.
TF = tempfile.NamedTemporaryFile(mode='a')
Where it seems to be failing, you are trying to read data from the file and put it in FT.
FT = np.loadtxt(TF,skiprows=0)
Change TF to mode='r' and you should have better luck.