yield 返回的数据相同

目的

从json中获取params和孙子级的id组合，获得如下格式的数据

data = [{},{},{}]

最后会提供完整的代码！

流程如下

方法一:

def get_cate_ids():
    ids = []
    with open("cate.txt", "rt",encoding='utf-8') as fp:
        for line in fp:
            data = json.loads(line)
            #判断是子集有数据
            if len(data['subcat'])>0:
                catLv1 = data["subcat"]
                for i in range(len(catLv1)):
                    #判断孙子级是否有数据
                    if len(catLv1[i]['subcat']) > 0:
                        catLv2 = catLv1[i]['subcat']
                        for j in range(len(catLv2)):
                            subids = {}
                            subids['params'] = data['params']
                            subids['id'] = catLv2[j]['id']
                            yield subids

方法二

def get_cate_ids():
    ids = []
    with open("cate.txt", "rt",encoding='utf-8') as fp:
        for line in fp:
            data = json.loads(line)
            subids = {}
            subids['params'] = data['params']
            if len(data['subcat'])>0:
                catLv1 = data["subcat"]
                for i in range(len(catLv1)):
                    if len(catLv1[i]['subcat']) > 0:
                        catLv2 = catLv1[i]['subcat']
                        for j in range(len(catLv2)):
                            subids['id'] = catLv2[j]['id']
                            yield subids

调用

ids = list(get_cate_ids())

方法一结果:

[{"params":"_version=1","id":"30020"},{"params":"_version=1","id":"30021"}]

方法二结果:

[{"params":"_version=1","id":"30021"},{"params":"_version=1","id":"30021"}]

发现由方法二产生的dict是相同的
Python用的不多，看了代码后有个模糊的感觉就是

for j in range(len(catLv2)):
    subids = {}
    subids['params'] = data['params']
    subids['id'] = catLv2[j]['id']
    yield subids

从表现来看法二中：i和j都已经是最大值

为什么会这样呢？在调试中，法二如果在在yield之前打印subids输出的也是正确的数据

代码示例：

import json

def get_cate_ids():
    ids = []
    line='{"name": "高中-通用技术", "params": "_version=1", "subcat": [{"id": 30019, "title": "苏教版", "hasChild": false, "subcat": [{"id": "30020", "title": "必修一", "hasChild": true}, {"id": "30021", "title": "必修2  技术与设计2", "hasChild": true}]}]}'
    data = json.loads(line)
    #判断是子集有数据
    subids = {}
    subids['params'] = data['params']
    if len(data['subcat'])>0:
        catLv1 = data["subcat"]
        for i in range(len(catLv1)):
            # 判断孙子级是否有数据
            if len(catLv1[i]['subcat']) > 0:
                catLv2 = catLv1[i]['subcat']
                for j in range(len(catLv2)):
                    # subids = {}
                    # subids['params'] = data['params']
                    subids['id'] = catLv2[j]['id']
                    yield subids

data = list(get_cate_ids())

print(data)