访问 Python 列表中的字典

Question

我有一个列表，其中包含这样的字典：json_obj = [[{'id': None},{'id': '5b98d01c0835f23f538cdcab'},{'id': '5b98d0440835f23f538cdcad'},{'id': '5b98d0ce0835f23f538cdcb9'}],[{'id': None},{'id': '5b98d01c0835f23f538cd'},{'id': '5b98d0440835f23f538cd'},{'id': '5b98d0ce0835f23f538cdc'}]]我希望它存储在这样的列表列表中：y=[['None','5b98d01c0835f23f538cdcab','5b98d0440835f23f538cdcad','5b98d0ce0835f23f538cdcb9'],['None','5b98d01c0835f23f538cd','5b98d0440835f23f538cd','5b98d0ce0835f23f538cdc']]为了从我尝试过的字典中读取 idfor d in json_obj:    print(d['id'])但是我在上面的代码中看到了这个错误：TypeError: list indices must be integers or slices, not str

Answer 1

您有一个嵌套的列表列表。有时有助于明显地观察这一点，注意嵌套[]语法：

json_obj = [[{'id': None}, {'id': 'abc'}, {'id': 'def'}, {'id': 'ghi'}],

            [{'id': None}, {'id': 'jkl'}, {'id': 'mno'}, {'id': 'pqr'}]]

您的语法适用于单个列表：

json_obj = [{'id': None}, {'id': 'abc'}, {'id': 'def'}, {'id': 'ghi'},

            {'id': None}, {'id': 'jkl'}, {'id': 'mno'}, {'id': 'pqr'}]

for d in json_obj:

    print(d['id'])

对于嵌套列表，您可以使用itertools.chain.from_iterable标准库中的：

json_obj = [[{'id': None}, {'id': 'abc'}, {'id': 'def'}, {'id': 'ghi'}],

            [{'id': None}, {'id': 'jkl'}, {'id': 'mno'}, {'id': 'pqr'}]]

from itertools import chain

for d in chain.from_iterable(json_obj):

    print(d['id'])

或者，如果没有导入，您可以使用嵌套for循环：

for L in json_obj:

    for d in L:

        print(d['id'])

Answer 2

使用嵌套列表理解。

json_obj = [[{'id': None},{'id': '5b98d01c0835f23f538cdcab'},{'id': '5b98d0440835f23f538cdcad'},{'id': '5b98d0ce0835f23f538cdcb9'}],[{'id': None},{'id': '5b98d01c0835f23f538cd'},{'id': '5b98d0440835f23f538cd'},{'id': '5b98d0ce0835f23f538cdc'}]]

print( [[j["id"] for j in i] for i in json_obj] )

或者

for i in json_obj:

    for j in i:

        print(j["id"])

输出：

[[None, '5b98d01c0835f23f538cdcab', '5b98d0440835f23f538cdcad', '5b98d0ce0835f23f538cdcb9'], [None, '5b98d01c0835f23f538cd', '5b98d0440835f23f538cd', '5b98d0ce0835f23f538cdc']]