variable is unsubscriptable when using [:] code example
Example: python value is unsubscriptable when using [:]
a = 1337
b = [1,3,3,7]
print b[0] # prints 1
print a[0] # raises your exception
a = 1337
b = [1,3,3,7]
print b[0] # prints 1
print a[0] # raises your exception