Let's define a list first:
lst=[1,2,3]
You can directly write your list to a file:
f=open("filename.txt","w")
f.write(str(lst))
f.close()
To read your list from text file first you read the file and store in a variable:
f=open("filename.txt","r")
lst=f.read()
f.close()
The type of variable lst is of course string. You can convert this string into array using eval function.
lst=eval(lst)