问如何在python中为嵌套列表和基本类型设置类型检查器？

EN

def is_list_of_list_of_int(a):
    return isinstance(a, list) and isinstance(a[0], list) and isinstance(a[0][0], int)

>>> is_list_of_list_of_int([[1,2,3],[2,3,4]])
True
>>> is_list_of_list_of_int(5)
False

def get_value_safe(a, i, j):
    try:
        return a[i][j]
    except TypeError:
        print('not a list of list')
        return None

>>> get_value_safe([[1,2,3],[2,3,4]], 1, 2)
4
>>> get_value_safe([1,2,3], 1, 2)
not a list of list

def typecheck(obj, *args):
    if isinstance(obj, args[0]):
        if len(args) == 1: # last one to check. Base case.
            return True
        if hasattr(args[0], "__iter__"): 
            #in other words, am I an iterator?
            for i in obj:
                if not typecheck(i, *args[1:]):
                    return False
            return True
     else: 
        return False

In [23]: typecheck([[3,3, "a"]],list, list, int)
Out[23]: False

In [24]: typecheck([[3,3]],list, list, int)
Out[24]: True

import __builtin__
def parse_spec(str_spec):
    return [getattr(__builtin__, x) for x in str_spec.rstrip('>').split('<')]

def validate(value, spec):
    for t in spec:
        if not isinstance(value, t):
            return False
        try:
            value = value[0]
        except TypeError:
            pass
    return True

>>> validate([10], parse_spec('list<int>'))
True
>>> validate([10], parse_spec('int'))
False
>>> validate([['something']], parse_spec('list<list<str>>'))
True