[issue4328] "à" in u"foo" raises a misleading error

[Ezio Melotti]

New submission from Ezio Melotti <ezio.melotti at gmail.com>:

With Python 2.x:
>>> 'à' in u'foo'
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: 'in <string>' requires string as left operand
>>> 'à' in u'xàx'
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: 'in <string>' requires string as left operand

The error claims that "'in <string>' requires string as left operand"
when actually the left operand *is* a string.

With Python2.6 with unicode_literals:
>>> print(b'\x85')
à
>>> b'\x85' in 'foo'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'in <string>' requires string as left operand

With Python3.x the error is slightly different:
TypeError: 'in <string>' requires string as left operand, not bytes

but then it works with:
>>> b'f' in 'foo'
True

This problem seems somehow related to the implicit decoding of 'à'. I
guess that 'à' in u'foo' should raise a UnicodeDecodeError ('xxx' codec
can't decode byte 0x85 ...), not a TypeError.

----------
components: Unicode
messages: 75907
nosy: ezio.melotti
severity: normal
status: open
title: "à" in u"foo" raises a misleading error
versions: Python 2.4, Python 2.5, Python 2.5.3, Python 2.6, Python 3.0

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue4328>
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