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import unittest
from io import StringIO
ENCODING = 'utf-8'
S0 = 'hello world, Umlauts: äöüßÄÖÜ, Chinese: 四是四，十是十，十四是十四，四十是四十，四十四隻不識字之石獅子是死的'
S0_BYTES = 'fe fi foe fam'.encode(ENCODING)
#print("###", StringIO, "###")
class TestStringIO(unittest.TestCase):
def test_001_text(self):
# If we throw unicode into the StringIO buffer, we'll
# get unicode out of it.
self.assertEqual(type(S0), str)
buf = StringIO()
print(S0, file=buf, end="")
s1 = buf.getvalue()
self.assertEqual(type(S0), type(s1))
self.assertEqual(S0, s1)
self.assertEqual(type(s1), str)
def test_002_bytes(self):
buf = StringIO()
print(S0_BYTES, file=buf, end="")
s1 = buf.getvalue()
# In Python 3 StringIO *ALWAYS* returns str (=text=unicode) !
# Even if we originally write bytes into the buffer, the value
# we get out of it has type str!
# Input is bytes
self.assertEqual(type(S0_BYTES), bytes)
# Output is NOT bytes...
self.assertNotEqual(type(S0_BYTES), type(s1))
self.assertNotEqual(type(s1), bytes)
# ...but str!
self.assertEqual(type(s1), str)
# So the contents are not equal!
self.assertNotEqual(S0_BYTES, s1)
# StringIO coerced bytes into str:
# b'xyz' ---> "b'xyz'"
self.assertEqual(str(S0_BYTES), s1)
# See, the type info is literally present in the output str!
self.assertEqual("b'" + str(S0_BYTES, encoding=ENCODING) + "'", s1)
# Coercion is NOT decoding!
self.assertNotEqual(S0_BYTES.decode(ENCODING), s1)
self.assertNotEqual(str(S0_BYTES, encoding=ENCODING), s1)
# These are the same
self.assertEqual(S0_BYTES.decode(ENCODING),
str(S0_BYTES, encoding=ENCODING))
# Additional note:
# If we do not specify an encoding when we create a StringIO
# buffer, Python 3 automatically uses the locale's preferred
# encoding: locale.getpreferredencoding()
# Cf. http://docs.python.org/release/3.0.1/library/io.html#io.TextIOWrapper
# In my case this is the same encoding as the encoding of this source file,
# namely UTF-8. If on your system both encodings are different, you may
# encounter other results than the above.
#
# In Python 3.2 the signature of StringIO() has changed. It is no more
# possible to specify an encoding here.
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