Michael Foord wrote:
[snip...]
Here is an example of getting a byte array from a binary pickle in
IronPython:
>>> import pickle
>>> class A(object):
... b = 'hello'
... c = (None, 'fish', 7.2, 7j)
... a = {1: 2}
...
>>> p = pickle.dumps(A(), protocol=2)
>>> p
u'\x80\x02c__main__\nA\nq\x00)\x81q\x01}q\x02b.'
>>> from System import Array, Byte
>>> a = Array[Byte](tuple(Byte(ord(c)) for c in p))
>>> a
Array[Byte]((<System.Byte object at 0x0000000000000033 [128]>,
<System.Byte obje...
And the converse:
>>> p2 = ''.join(chr(c) for c in a)
>>> a2 = pickle.loads(p2)
>>> a2
<A object at 0x000000000000004E>
>>> a2.a
{1: 2}
>>> a2.b
'hello'
>>> a2.c
(None, 'fish', 7.2, 7j)
Michael
I hope this is at least slightly helpful. :-)
Michael
My basic issue is that the 'str' unavoidably implies certain
semantics when
calling .NET APIs from IronPython. These APIs interpret str as text
rather
than just bytes, which therefore gets transformed by various text
encodings,
such as UTF-8 to UTF-16. Such encodings are undesirable for my
pickled data
since the result is no longer necessarily a valid pickle. I suppose
the
intention in Python 3.0 is that 'bytes' doesn't carry any semantics
with it,
its just data, which is why pickle.dumps() in Python 3.0 returns bytes
rather than str.
I want to push plain old byte arrays into the database from both
CPython and
IronPython, so I can avoid any head-scratching confusion with database
adapters and/or databases inappropriately encoding or decoding my data.
For example "data = [ord(c) for c in some_string]" has behaved as
expected many times for me in IronPython (and could help you turn
strings into bytes).
Thanks. I'll try something based on that.
Is this a theoretical problem at this stage or an actual problem?
Its an actual problem with SQLiteParameter.Value from the SQLite ADO.NET
provider. I think our original CPython code is a bit sloppy with
respect to
the distinction between text strings and byte arrays, so I'll
probably need
to tighten things up on both sides.
Would you agree tha using unicode() and bytes() everywhere and avoiding
str() gives code that has the same meaning in Python 2.6, IronPython
2.6 and
Python 3.0? Do you think this would be a good guideline to follow
until we
can leave Python 2.x behind?
Many thanks,
Rob
--
http://www.ironpythoninaction.com/
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