TypeError: '_TemporaryFileWrapper' object is not an iterator

[Antoon Pardon]

Below is a short program that illustrate the problem
It works with python2, whether you use the -c option or not.
It only works with python3 if you use the -c option.

The problem seems to come from my expectation that a file
is its own iterator and in python3 that is no longer true
for a NamedTemporaryFile.

Should this be considered a bug?
 
=========================================================================

from tempfile import NamedTemporaryFile
import sys

def main(tmp):
	write = sys.stdout.write
	if tmp:
		tstfl = NamedTemporaryFile("w+", prefix = 'tmptest-')
	else:
		tstfl = open("Temporary", "w+")

	for nr in range(10):
		tstfl.write("This is line %d\n" % nr)

	tstfl.seek(0)
	try:
		while True:
			ln = next(tstfl)
			write(ln)
	except StopIteration:
		pass

if __name__ == "__main__":
	tmp = True
	if len(sys.argv) > 1:
		# if -c option is passed a normal file will be
		# used instead of a NamedTemporaryFile
		if sys.argv[1] == '-c':
			tmp = False 
	main(tmp)