python中使用jsonpath提取数组长度（length）的方法

我有一个如下的json，想要用jsonpath获取content列表中元素的个数，如下应该是2个。python中使用代码中的表达式获取不到，但是在http://jsonpath.com/ 上表达式是可以用的，谁知道是怎么回事吗。

d={
    "code": "ok",
    "data": {
        "content": [{
            "id": 93,
            "mark": "test001",
            "consumer": "测试"
        }, {
            "id": 94,
            "mark": "test002",
            "consumer": "测试"
        }],
        "last": 1
    }
}
c='{"code": "ok","data": {"content": [{"id": 93,"mark": "test001","consumer": "测试"},{"id": 94,"mark": "test002","consumer": "测试"}],"last": 1}}'
c=json.loads(c)
print(jsonpath.jsonpath(c,"$..content.length")) #实际返回false
print(jsonpath.jsonpath(d,"$..content.length")) #实际返回false

需要调用两个库吧json，jsonpath

import json
import jsonpath
d={
    "code": "ok",
    "data": {
        "content": [{
            "id": 93,
            "mark": "test001",
            "consumer": "测试"
        }, {
            "id": 94,
            "mark": "test002",
            "consumer": "测试"
        }],
        "last": 1
    }
}
c='{"code": "ok","data": {"content": [{"id": 93,"mark": "test001","consumer": "测试"},{"id": 94,"mark": "test002","consumer": "测试"}],"last": 1}}'
c=json.loads(c)
print(jsonpath.jsonpath(c,"$..content.length")) #实际返回false
print(jsonpath.jsonpath(d,"$..content.length")) #实际返回false

可以看下这个博客