[igraph] problems with write function

[Matteo Zandi]

Hi,

I'm using the igraph 0.5.1 python bindings, I have some problems with the write function. First, adjacency format is not recognized unless called directly:

>>> g = igraph.Graph.Barabasi(10, 15, directed=False)
>>> igraph.plot(g, 'test.png')
<igraph.drawing.Plot object at 0xb6fc696c>
>>> g.write_adjacency('/tmp/test.adj')
>>> g.write('/tmp/test.adj')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.5/site-packages/igraph/__init__.py", line 1135, in write
    raise IOError, "unknown file format: %s" % str(format)
IOError: unknown file format: None

Secondly, with other formats (ncol, pajek, dot, etc) it is able to recognize automatically the format with the extension of the file, but pajek crashes with 

python: igraph_strvector.c:121: igraph_strvector_get: Assertion `sv->data != 0' failed.

attached you can find the dot and pickle format of the graph that causes igraph to crash.

Thanks,
Matteo

obama.dot
Description: MS-Word document

obama.pickle
Description: Binary data