Question

for a in map:
    for b in map[a]:
        for c in map[b]:
            for d in map[c]:
                for e in map[d]:
                    print a+b+c+d+e

The above code is used to create all paths of certain length in a graph.
map[a] represents the points you can reach from point a.

How can I change it to simulate having an arbitrary number of loops?

This is like a cartesian product (itertools.product) where at each iteration
your choice for the next element is limited to those in map[current_point].

Answer 1

map = {
    'a': ['b', 'c'],
    'b': ['c', 'd'],
    'c': ['d', 'a'],
    'd': []
}

def print_paths(map, start, length, prefix = ''):
    if length == 0:
        print prefix
    else:
        for a in map[start]:
            print_paths(map, a, length - 1, prefix + start)

for a in map.keys():
    print_paths(map, a, 5)