Ni! Hi ashu,
Please, always try to *read errors carefully* and consult the documentation. Not to mention, provide self-contained examples.
Python is throwing a "TypeError" and telling you it expects an integer ('unsigned long', the C++ type for vertex indices) while you are passing it a string ('str').
As you can see
in the documentation, if you want to pass strings to add_edge_list you should set two additional arguments: `hash=True` and `string_vals=True`.
If that doesn't fix it, you'll have to provide a self-contained example where the error occurs, otherwise we can't really help.
.~´