# Avoiding Recursion

Occasionally I implement an algorithm recursively then hit the recursion limit in Python.

For example, I just wrote this:

```def clique(self, node, done=None):
if done is None:
done = set()
done.add(node)
for other_node in self.edges_by_node[node]:
if other_node not in done:
self.clique(other_node, done)
return done
```

which hits a limit if the graph is too big.

So I rewrote it like this:

```def clique(self, start_node):
done = set()
to_do = [start_node]
while to_do:
node = to_do.pop()
done.add(node)
for other_node in self.edges_by_node[node]:
if other_node not in done:
to_do.append(other_node)
return done
```

There's a simple relationship between the two, quite independent of the specific task at hand. Which got me thinking about abstracting the specific task out of the recursive versus non-recursive pattern.

I guess I was having an SICP moment :-)

The original post was in the categories: python algorithms but I'm still in the process of migrating categories over.

The original post had 1 comment I'm in the process of migrating over.