Traversing a dictionary recursively

Question

I need to traverse a dictionary recursively and remember the previous keys.

Let me explain:

dic = {u'resources': {u'info': {u'load': (u'37', u'17')}}, u'peak': {u'load': (u'0', u'1')}}

The elements are always a value or a dictionary until it reaches a value. I want to print the above dic like this: (omit the xxx below, it should eventually be a diff of the two values)

resources info load 37 17 xxx
resources peak load 0 1 xxx

This is the code I have so far:

def convertToTable(var):
    if isinstance(var, tuple):
        if len(var) != 2:
            return str(var)

        v1, v2 = var
        try:
            v1 = float(v1)
            v2 = float(v2)
        except ValueError:
            pass
        if type(v1) != type(v2):
            return '\t%s\t%s\n' % (v1, v2)
        elif isinstance(v1, int) or isinstance(v1, float):
            sign = '+' if v2 - v1 > 0 else ''
            return '\t%s\t%s\t%s%s\n' % (v1, v2, sign, v2 - v1)
        elif isinstance(v1, list):
            ret = ''
            for i in range(max(len(v1), len(v2))):
                v1v = v1[i] if i < len(v1) else ''
                v2v = v2[i] if i < len(v2) else ''
                ret += '\t%s, %s\n' % (v1v, v2v)
            return ret
        else:
            return '\t%s\t%s\n' % (v1, v2)
    elif isinstance(var, dict):
        ret = ''
        for key, value in var.iteritems():
            # fix this crap, it's not printing all recursive levels of keys!
            ret += '%s %s' % (key, convertToTable(value))
        return ret
    else:
        return '%s\n' % (var)

I don´t know how to pass the previous keys recursively to the function again! Either I get an extra print of keys or nothing! (please do not advice me that I should use json.dumps as it does not really do what I need!) I am hoping someone can check my solution and point out the flaw in it!

Answer 1

I'm not sure what's wrong with your code, but this might do what you want:

def iteritems_recursive(d):
  for k,v in d.iteritems():
    if isinstance(v, dict):
      for k1,v1 in iteritems_recursive(v):
        yield (k,)+k1, v1
    else:
      yield (k,),v

dic = {u'resources': {u'info': {u'load': (u'37', u'17')}, u'peak': {u'load': (u'0', u'1')}}}

for p,v in iteritems_recursive(dic):
  print p, "->", v

iteritems_recursive iterates over the passed-in dictionary, and returns a a (path, value) tuple. The path is itself a tuple which describes the keys that reach that item.

The above code prints:

(u'resources', u'info', u'load') -> (u'37', u'17')
(u'resources', u'peak', u'load') -> (u'0', u'1')

If you want to print the table pretty, replace the for loop above with this:

for p,v in iteritems_recursive(dic):
  diff = float(v[0]) - float(v[1])
  p = ''.join('{:10}'.format(w) for w in p)
  v = ''.join('{:5}'.format(f) for f in v)
  print p, v, diff

Which prints:

resources info      load       37   17    20.0
resources peak      load       0    1     -1.0