python字典添加元素

比如我新建一个字典s
s = {}
然后往立面添加元素，但是提示KeyError: 'aaaa'
s['aaaa']['a']='4444444'
s['aaaa']['b']='11111'
s['aaaa']['c']='22222'
s['aaaa']['d']='33333'
s['bbbb']['a']='aaaaa'
s['bbbb']['b']='werwer'

php可以这样给二维数组赋值，python就不行，请问代码该怎么写ne？

---

Python在执行语句s['aaaa']['a']='4444444'时，
先要获取s['aaaa'], 再往s['aaaa']中添加元素，
但是因为s是一个空字典，所以获取s['aaaa']时会出现错误提示KeyError: 'aaaa'

改正的写法可以是：

s = {}
s['aaaa'] = {}
s['aaaa']['a'] = '4444444'
s['aaaa']['b'] = '11111'

---

>>s={}
>>s['aaaaa']='44444'
>>s
output {'aaaaa':'44444'}

题主说答案不符合要求

>>s={}
>>s['aaaaa']={}
>>s['aaaaa']['a']={1}
>>s
output{'aaaaa':{'a':1}}

这样？

---

s.setdefault('aaaa', {})['a']  = 1

---

s = {}
s["aaaa"] = {}

......