Re: [igraph] Re: Loading from a string or file IO object in Python

[Tamas Nepusz]

> 1. Is 'PyString_AsString' portable?
Yes it is, because it merely converts between a Python string and a C- 
style string (more precisely, it returns a pointer to the internal  
storage area of a Python string -- this should be kept intact).

The real problem lies here (as Gabor stated):

> 2. I think the cString would not work, because the igraph functions
> expect a FILE* and they want to call 'fread' (fscanf, etc.) on it.

A possible way to go is to write the string to a temporary file and  
read that back -- another alternative is fmemopen() or  
open_memstream(), but we have to implement the temporary file solution  
anyway because of portability issues. Chris, if you feel like you have  
the courage to patch the source code of the Python interface, go on ;)  
I have two possibilities in mind:

1. We could add another function to convert.c (say,  
igraphmodule_PyString_or_PyFile_to_fileptr()) that always returns an  
appropriate file pointer -- although we also have to take care of  
cleaning up the temporary file at some point.

2. We could simply override IO-related methods one level "above" in  
the Python layer (remember, the C layer implemeents  
igraph.core.GraphCore, igraph.Graph is inherited from that) to handle  
strings and files appropriately. This way we could maybe also handle  
URLs (i.e., if the string given is a URL, igraph could open a network  
connection and use the socket).

--
Tamas