Question

Data: a dependency list, already verified to be acyclic. So here, ‘a’ depends on ‘b’,’c’ (c depends on d), etc…

A = { 'a' :  dict(b=1, c=1),     'c' : dict(d=1),     'd' : dict(e=1,f=1,g=1),     'h' : dict(j=1)     } 

I’d like to have a top-down, recursive solution to let’s say, find the chain starting at ‘a’: a, c, d, e, g, f, b

So, right now (a non-generator solution):

def get_all(D,k):     L = []     def get2(D,k):         L.append(k)         for ii in D.get(k,[]):             get2(D, ii)     get2(D,k)     return L 

Obviously, this is pretty weak 🙂 I’ve been banging my head about how to how to get yields inside there, and I’d appreciate any py-foo y’all can bring to this.

Answer 1

Try this:

#!/usr/bin/env python  def get_all(D, k):     yield k     for ii in D.get(k, []):         for jj in get_all(D, ii):             yield jj  A = { 'a' : dict(b=1, c=1),     'c' : dict(d=1),     'd' : dict(e=1,f=1,g=1),     'h' : dict(j=1)     }  for ii in get_all(A,'a'):     print ii 

Gives me

 steve@rei:~/code/tmp $ python recur.py a c d e g f b