Don't use argument unpacking on strings

[eric-wieser]

struct.pack('5s', b'abcde') works just fine for me on 3.5.0. Argument unpacking a string is going to be a big performance hit for long strings too

[eric-wieser]

Ouch!

In [1]: import struct
In [2]: data = b" "*100000

In [3]: % timeit struct.pack('100000s',data)  # with this patch
The slowest run took 4.30 times longer than the fastest. This could mean that an intermediate result is being cached
100000 loops, best of 3: 15.3 µs per loop

In [4]: % timeit struct.pack('100000B',*data)  # without it
100 loops, best of 3: 7.48 ms per loop

[eric-wieser]

And at the extreme:

In[1]: import struct
In[2]: data = b" " * 1000000000
In[3]: %timeit struct.pack('s', data)
The slowest run took 7.66 times longer than the fastest. This could mean that an intermediate result is being cached
1000000 loops, best of 3: 487 ns per loop
In[4]: %timeit struct.pack('B', *data)
MemoryError

[dirk-thomas]

Invalid syntax: lacks trailing ).

[eric-wieser]

Thanks! I had no idea why the marker was pointing at the start of the line in the traceback

[eric-wieser]

I think it would make a lot more sense for every assertion in this test of be of the form self.assertEqual(expectedValue, eval(default_value)), rather than making requirements about the exact format of the python source code. Thoughts?

[eric-wieser]

These tests now fail because the python output of the generator has changed. At some point I'll update the expected output files to match the new output

[dirk-thomas]

Thank you for the patch. Merged to kinetic-devel in #63.