I am sorry but it seems we haven't defined the the first_graph variable.
Traceback (most recent call last):
File "file-reader.py", line 12, in <module>
for name in first_graph.vs["name"]:
NameError: name 'first_graph' is not defined
Sorry, I am really embarrassed asking many questions :(
-Ahmed
On Sun, Nov 17, 2013 at 4:52 AM, Tamás Nepusz <[email protected]> wrote:
> One of your CSV files does not have a “source” header for sure.
>
> --
> T.
>
> On Sunday, 17 November 2013 at 01:28, Ahmed Abdeen Hamed wrote:
>
> Thank you!
>
> It is not liking the headers of the csv files:
>
>
> Ahmeds-MacBook-Pro:python-projects ahamedCOM$ python file-reader.py
> Traceback (most recent call last):
> File "file-reader.py", line 8, in <module>
> g = Graph.DictList(vertices=None, edges=chain(reader1, reader2))
> File "/Library/Python/2.7/site-packages/igraph/__init__.py", line 2246,
> in DictList
> v1 = vertex_name_map[edge_data[efk_src]]
> KeyError: 'source'
>
>
> -Ahmed
>
>
>
>
>
>
> On Sat, Nov 16, 2013 at 11:32 AM, Tamás Nepusz <[email protected]> wrote:
>
> Hi,
>
> How do you append to a graph from a file?
>
> Here is a scenario of what I am trying to do I have two different csv
> files:
>
> 1. How about concatenating the two files first and then loading the
> combined file?
>
> 2. If you don’t want to concatenate the physical files, you can still
> concatenate the CSV reader objects that you use to read them:
>
> from itertools import chain
>
> reader1 = csv.DictReader(open(“file1.csv”))
> reader2 = csv.DictReader(open(“file2.csv”))
> g = Graph.DictList(vertices=None, edges=chain(reader1, reader2))
>
> 3. If you already have a graph and you want to add edges from another file
> to it, you will need a lookup table that 1) maps vertex names from the
> first graph to the corresponding vertex IDs, 2) is able to create new IDs
> for vertex names from the second that it hasn’t seen yet. igraph’s
> UniqueIdGenerator object can help you with that:
>
> # Create the UniqueIdGenerator and pre-load it with the names from the
> first graph
> id_gen = UniqueIdGenerator()
> for name in first_graph.vs[“name”]:
> id_gen.add(name)
>
> # Read the second graph
> reader = csv.DictReader(open(“file2.csv”))
> new_edges = []
> for row in reader:
> new_edges.append(id_gen[row[“source”]], id_gen[row[“target”]])
>
> # Add the new vertices and edges to the graph
> n = g.vcount()
> if n < len(id_gen):
> g.add_vertices(len(id_gen) - n)
> g.vs[“name”] = id_gen.values()
> g.add_edges(new_edges)
>
> I know that it’s a bit cumbersome; the Python interface desperately needs
> a Graph.union_by_name() function but I haven’t had time to add it yet.
>
> —
> T.
>
>
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