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Subject: Re: networkx plot random graph Error
From: Jason Swails <jason.swails@gmail.com>
In-Reply-To: <0d48b8fc-0ed0-434f-8004-5e0ff3693171@googlegroups.com>
Date: Wed, 16 Jul 2014 20:24:37 -0700
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To: u2107 <phani.lav@gmail.com>
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On Jul 15, 2014, at 3:11 AM, u2107 <phani.lav@gmail.com> wrote:

> I am trying to read a file with 3 columns with col 1 and 2 as =
nodes/edges and column 3 as weight (value with decimal)
>=20
> I am trying to execute this code=20
>=20
>=20
> import networkx as nx
>=20
>=20
> G =3D nx.read_edgelist('file.txt', data=3D[("weight")])
> G.edges(data=3DTrue)
>=20
> edge_labels =3D dict(((u, v), d["weight"]) for u, v, d in =
G.edges(data=3DTrue))
> pos =3D nx.random_layout(G)
> nx.draw(G, pos)
> nx.draw_networkx_edge_labels(G, pos, edge_labels=3Dedge_labels)
>=20
> import matplotlib.pyplot as plt; plt.show()
>=20
>=20
>=20
> Error:=20
>=20
> File "graph_one.py", line 4, in <module>
>    G =3D nx.read_edgelist('File.txt', data=3D[("weight")])
>  File "<string>", line 2, in read_edgelist
>  File =
"/usr/local/lib/python2.7/dist-packages/networkx-1.7-py2.7.egg/networkx/ut=
ils/decorators.py", line 241, in _open_file
>    fobj =3D _dispatch_dict[ext](path, mode=3Dmode)
> IOError: [Errno 2] No such file or directory: =
'contactUSC_nodes_diff_small.txt'

This looks like some file didn't exist which probably should have.  The =
next line looks like you may have fixed the problem and then run the =
command again?  Is this part of the error message?  Including stuff like =
this is confusing (to me, at least).

> lavanya@peerformance:~/Desktop/INRIA_Papers/Python$ python =
graph_one.py
> Traceback (most recent call last):
>  File "graph_one.py", line 4, in <module>
>    G =3D nx.read_edgelist('contactUSC_node_diff_small.txt', =
data=3D[("weight")])
>  File "<string>", line 2, in read_edgelist
>  File =
"/usr/local/lib/python2.7/dist-packages/networkx-1.7-py2.7.egg/networkx/ut=
ils/decorators.py", line 263, in _open_file
>    result =3D func(*new_args, **kwargs)
>  File =
"/usr/local/lib/python2.7/dist-packages/networkx-1.7-py2.7.egg/networkx/re=
adwrite/edgelist.py", line 367, in read_edgelist
>    data=3Ddata)
>  File =
"/usr/local/lib/python2.7/dist-packages/networkx-1.7-py2.7.egg/networkx/re=
adwrite/edgelist.py", line 286, in parse_edgelist
>    for (edge_key,edge_type),edge_value in zip(data,d):
>=20
> ValueError: too many values to unpack

Collections in python can be "unpacked" using a specific syntax that =
assigns a tuple of individual variables (or names) to a collection =
(these can be nested).  If there are too many or too few single names, a =
ValueError gets thrown.  Consider:

py> col =3D [1, 2, 3]
py> a, b, c =3D col
py> print("{0} {1} {2}".format(a, b, c))
1 2 3
py> a, b =3D col
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack
py> a, b, c, d =3D col
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 3 values to unpack

The traceback for this exception ends inside the networkx code and =
either indicates a bug in the networkx code or an input error that is =
not gracefully handled.

My suggestions are twofold:

1) Upgrade to the latest release.  If this is a bug, it's very possible =
that it was fixed in later releases (1.7 is over 2 years old and there =
have been a couple major releases since then.

2) Sign up for the networkx mailing list and ask your question there.  =
You are certain to get a faster and more relevant answer. (See the =
"mailing list" link here: http://networkx.github.io/)

Hope this helps,
Jason