python RuntimeError: dictionary changed size during iteration
<p>I have obj like this</p>

<pre><code>{hello: 'world', "foo.0.bar": v1, "foo.0.name": v2, "foo.1.bar": v3}
</code></pre>

<p>It should be expand to </p>

<pre><code>{ hello: 'world', foo: [{'bar': v1, 'name': v2}, {bar: v3}]}
</code></pre>

<p>I wrote code below, splite by <code>'.'</code>, remove old key, append new key if contains <code>'.'</code>, but it said <code>RuntimeError: dictionary changed size during iteration</code></p>

<pre><code>def expand(obj):
    for k in obj.keys():
        expandField(obj, k, v)

def expandField(obj, f, v):
    parts = f.split('.')
    if(len(parts) == 1):
        return
    del obj[f]
    for i in xrange(0, len(parts) - 1):
        f = parts[i]
        currobj = obj.get(f)
        if (currobj == None):
            nextf = parts[i + 1]
            currobj = obj[f] = re.match(r'\d+', nextf) and [] or {}
        obj = currobj
    obj[len(parts) - 1] = v
</code></pre>

<p>for k, v in obj.iteritems():</p>

<p>RuntimeError: dictionary changed size during iteration</p>
