#!/usr/bin/env python3
import tempfile, io
smiley = '\u263a'           # A Unicode smiley character
spool = tempfile.SpooledTemporaryFile(max_size=5, mode='w+', encoding='utf-8')
spool.write(smiley*10)      # Gets written to io.StringIO, then forces rollover to TemporaryFile
# Uncomment the following to circumvent the bug
#spool.seek(0, io.SEEK_END)  # Force current position to end of TemporaryFile
spool.write(smiley*10)      # Overlays some previous bytes because of bug
spool.seek(0)               # Prepare to read back what we wrote
data = spool.read()
print('We read', data)
if data == smiley*20:
    print('It matches what we wrote')
else:
    print('It doesn\'t match what we wrote')