{'name_first': ['abc'], 'name_last': ['def'], 'name_info_login': ['aaa1'], 'name_info_descr': ['aaa2'],'email':['abc@def.gh']}

{
  'name': {
    'first': 'aaaa',
    'last': 'bbbb',
    'info': {
      'login': 'aaa1',
      'desct': 'aaa2'
    },
    'email': 'abc@def.gh'
  }
}

def parse_post(post):
    out = {}
    for (key, value) in post.items():
        if value[0] == '': continue
        if '_' in key:
            key = key.split('_')
            if not key[0] in out: out[key[0]] = {}  #это две строчки нужно както оптимизировать)
            out[key[0]][key[1]] = [value[0]] #это две строчки нужно както оптимизировать)
        else:
            out[key] = [value[0]]
    return out

din = {'name_first': ['abc'], 'name_last': ['def'], 'name_info_login': ['aaa1'], 'name_info_descr': ['aaa2'],'email':['abc@def.gh']}
def parse_post(post):
    out = {}
    for ki, v in post.viewitems():
        td, ln = out, ki.split('_')
        for k in ln[:-1]:
            td = td.setdefault(k, {})
        td[ln[-1]] = v[0]
    return out
print parse_post(din)