How to loop a list and append it to a dictionary in a loop?

Question

It is for a dynamic ring topology project. Specifically, I need to name each node: s1,s2...sz, and name each host h1-1,h1-2,...hz-n. So z is the number of the nodes, and n is the number of the host connected to each node. So I have a list of the nodes, I am trying to use the node as a key to have another list of hosts, then I can put them in a dictionary for use. Just how can I achieve this goal? The example graph is as below:

What have you tried doing? Show your code and explain where exactly you are struggling with it. (Also why did you put a "node.js" tag?) — UnholySheep, Jan 14 '17 at 22:02
I am trying to build a Dynamic Mininet Topology. So I have posted the code below. — angelionmaker, Jan 14 '17 at 22:54
My code was too long... I will try the solution from below first... Thanks... — angelionmaker, Jan 14 '17 at 22:58

score 0 · Accepted Answer · answered Jan 14 '17 at 22:44

I think you are looking for something along the lines of this:

# run with python dynamictopo.py z n
# e.g.: python dynamictopo.py 3 2
import sys

z = int(sys.argv[1])  # number of nodes
n = int(sys.argv[2])  # number of hosts

nodes = []
for i in range(0, z):
    nodes.append("s" + str(i + 1))

print(nodes)

dct = {}
for j, node in enumerate(nodes):
    hosts = []
    for h in range(0, n):
        hosts.append("h" + nodes[j][1] + "-" + str(h + 1))
    dct[node] = hosts

print(dct)

This will print ['s1', 's2', 's3'] and {'s2': ['h2-1', 'h2-2'], 's3': ['h3-1', 'h3-2'], 's1': ['h1-1', 'h1-2']} if you use 3 and 2 as command line arguments. Note that dictionaries are unordered.

Or use this:

# run with python dynamictopo.py z n
# e.g.: python dynamictopo.py 3 2
import sys

z = int(sys.argv[1])  # number of nodes
n = int(sys.argv[2])  # number of hosts

dct = {}
for i in range(z):
    hosts = []
    for h in range(0, n):
        hosts.append("h" + str(i + 1) + "-" + str(h + 1))
    dct["s" + str(i + 1)] = hosts

print(dct)

No problem. As you are new here: you might want to select my answer instead of commenting. — Spherical Cowboy, Jan 14 '17 at 23:05
just the follow up, I encountered a syntax error, which is as below... do you know the reason? dct = {} ^ SyntaxError: invalid syntax — angelionmaker, Jan 15 '17 at 02:47
Oh, I copied the error comment. So ^ is below the dct. If I run the code above, it runs perfectly. The error only occurs when I am applying this to my project.... — angelionmaker, Jan 15 '17 at 03:23

How to loop a list and append it to a dictionary in a loop?

1 Answers1