python 如何處理提取嵌套中括弧 [] 的內容?

import re
b = "[[1,2,344],[323,3,34]]"

regex1 = re.compile(r[[(.*)]])
print (regex1.findall(b))
#提取括弧內的數字，保存順序不變。


"""方法一"""
str_ = "[[1,2,344],[323,3,34]]"
list_ = eval(str_)
[i for k in list_ for i in k]

""""方法二"""
import re
string = "[[1,2,344],[323,3,34]]"
regex = re.compile(d+)
[int(i) for i in re.findall(regex, string)]


&>&>&> b = "[[1,2,344],[323,3,34]]"
&>&>&> b.replace([,).replace(],).split(,)
[1, 2, 344, 323, 3, 34]