List and order

[Nic]

Hello,
I'm using the NetworkX Python package (https://networkx.lanl.gov/).
Through this package I wrote the following code:

import networkx as NX
G=NX.Graph()
G.add_edge(1,2)
G.add_edge(2,3)
G.add_edge(3,4)
ddeg=G.degree(w ith_labels=True )
for (u,v) in G.edges():
print ddeg[u],ddeg[v]

As result, I have:

12
22
21

I'd like to order the numbers included in the couples in a decrescent way:

12
12
22

And then to write the couples on a single line, always in a decrescent way:
12 12 22

I'm not able to do this operation. Can you help me please?
Thanks a bunch,
Nic

[Miki]

Re: List and order

Hello Nic,

Python lists has a very powerfull buid-in "sort".

edges = list(G.edges())
edges.sort(key = lambda u, v: (ddeg(u), ddeg(v)))
for u, v in edges:
print u,v, # Note the training comma to avoid newline
print

HTH,
Miki

http://pythonwise.blogspot.com

[Nic]

Re: List and order

Hello Miki,

Many thanks for the support.
I tried to insert and execute the code, but the following error happens:

Traceback (most recent call last):
File "grafodna.p y", line 10, in ?
edges.sort(key = lambda u, v: (ddeg(u), ddeg(v)))
TypeError: <lambda>() takes exactly 2 arguments (1 given)

Do you know how is it possible to delete it?
Thanks.

Nic

"Miki" <miki.tebeka@gm ail.com> ha scritto nel messaggio
news:1147691967 .998184.285120@ u72g2000cwu.goo glegroups.com.. .[color=blue]
> Hello Nic,
>
> Python lists has a very powerfull buid-in "sort".
>
> edges = list(G.edges())
> edges.sort(key = lambda u, v: (ddeg(u), ddeg(v)))
> for u, v in edges:
> print u,v, # Note the training comma to avoid newline
> print
>
> HTH,
> Miki
> http://pythonwise.blogspot.com
>[/color]

[Peter Otten]

Re: List and order

Nic wrote:
[color=blue]
> I tried to insert and execute the code, but the following error happens:
>
> Traceback (most recent call last):
> File "grafodna.p y", line 10, in ?
> edges.sort(key = lambda u, v: (ddeg(u), ddeg(v)))
> TypeError: <lambda>() takes exactly 2 arguments (1 given)
>
> Do you know how is it possible to delete it?[/color]

Note that

lambda a, b: ...

takes two arguments while

lambda (a, b): ...

takes one argument which must be a sequence (list, string, generator,...) of
two items.

So the above should probably be

edges = list(G.edges())
edges.sort(key= lambda (u, v): (ddeg[u], ddeg[v]))
for u, v in edges:
print ddeg[u], ddeg[v],
print


Here's how I would do it:

edges = [(ddeg[u], ddeg[v]) for u, v in G.edges()]
edges.sort()
for a, b in edges:
print a, b,
print

(all untested)

Peter

[Nic]

Re: List and order

Many thanks.
Both the cases are OK.
The only problem is that from:
12
22
21
In spite of writing
12 12 22
it writes
12 21 22
Do you know how is it possible to delete also this last trouble?
Thanks a bunch,
Nic

"Peter Otten" <__peter__@web. de> ha scritto nel messaggio
news:e49u2k$3i2 $02$1@news.t-online.com...[color=blue]
> Nic wrote:
>[color=green]
>> I tried to insert and execute the code, but the following error happens:
>>
>> Traceback (most recent call last):
>> File "grafodna.p y", line 10, in ?
>> edges.sort(key = lambda u, v: (ddeg(u), ddeg(v)))
>> TypeError: <lambda>() takes exactly 2 arguments (1 given)
>>
>> Do you know how is it possible to delete it?[/color]
>
> Note that
>
> lambda a, b: ...
>
> takes two arguments while
>
> lambda (a, b): ...
>
> takes one argument which must be a sequence (list, string, generator,...)
> of
> two items.
>
> So the above should probably be
>
> edges = list(G.edges())
> edges.sort(key= lambda (u, v): (ddeg[u], ddeg[v]))
> for u, v in edges:
> print ddeg[u], ddeg[v],
> print
>
>
> Here's how I would do it:
>
> edges = [(ddeg[u], ddeg[v]) for u, v in G.edges()]
> edges.sort()
> for a, b in edges:
> print a, b,
> print
>
> (all untested)
>
> Peter[/color]

[Peter Otten]

Re: List and order

Nic wrote:
[color=blue]
> The only problem is that from:
> 12
> 22
> 21
> In spite of writing
> 12 12 22
> it writes
> 12 21 22
> Do you know how is it possible to delete also this last trouble?[/color]

I thought that the two 12 were a typo, but it seems you want to reorder the
nodes inside an edge, too. Here's a fix that normalizes the edge before
sorting the list of edges:

edges = [sorted((ddeg[u], ddeg[v])) for u, v in G.edges()]
edges.sort()
for a, b in edges:
    print a, b,
print

Peter

[Nic]

Re: List and order

Perfect. Thanks.
Nic

"Peter Otten" <__peter__@web. de> ha scritto nel messaggio
news:e4aahn$l16 $01$1@news.t-online.com...[color=blue]
> Nic wrote:
>[color=green]
>> The only problem is that from:
>> 12
>> 22
>> 21
>> In spite of writing
>> 12 12 22
>> it writes
>> 12 21 22
>> Do you know how is it possible to delete also this last trouble?[/color]
>
> I thought that the two 12 were a typo, but it seems you want to reorder
> the
> nodes inside an edge, too. Here's a fix that normalizes the edge before
> sorting the list of edges:
>
> edges = [sorted((ddeg[u], ddeg[v])) for u, v in G.edges()]
> edges.sort()
> for a, b in edges:
> print a, b,
> print
>
> Peter
>
>[/color]