如何从过滤器的字典列表中提取数据

Question

我有一个字典列表，它是从论坛中抓取的 HTML 元素：

[{'title': 'aaa', 'responses': '1 response', 'url': 'https://www.example.com/aaa'}, {'title': 'bbb', 'responses': '4 responses', 'url': 'https://www.example.com/bbb'}, {'title': 'ccc', 'responses': '2 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'ddd', 'responses': '8 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'eee', 'responses': '2 responses', 'url': 'https://www.example.com/eee'}]

如果 'reponses' 项小于 2 个响应，我想从字典中提取 'url' 项。 我尝试了这段代码，它运行良好，但仅适用于第一项：

dict = {'url1': ''}
item1 = "1 response"
item2 = "2 responses"
if item1 in scrape[0]['responses'] or item2 in scrape[0]['responses']:
    dict['url1'] = scrape[0]['url']
    print(dict)

{'url1': 'https://www.example.com/aaa'}

如果我删除 [0] 元素，我会得到：TypeError: list indices must be integers or slices, not str

我想要这个结果：

{'url1': 'https://www.example.com/aaa', 'url2': 'https://www.example.com/eee'}

如何做到这一点？

Answer 1

你可以写一个函数，用filter(...)就行了：

lst = [{'title': 'aaa', 'responses': '1 response', 'url': 'https://www.example.com/aaa'}, {'title': 'bbb', 'responses': '4 responses', 'url': 'https://www.example.com/bbb'}, {'title': 'ccc', 'responses': '2 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'ddd', 'responses': '8 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'eee', 'responses': '2 responses', 'url': 'https://www.example.com/eee'}]

def few_responses(item):
    number, _ = item['responses'].split()
    if (int(number) < 2):
        return True
    else:
        return False


for item in filter(few_responses, lst):
    print(item["url"])

或者，您可以使用执行相同操作的列表推导：

urls = [item["url"]
        for item in lst
        for number, _ in [item["responses"].split()]
        if (int(number) < 2)]
print(urls)

Answer 2

这是一种使用简单迭代的方法，str.split

例如：

data = [{'title': 'aaa', 'responses': '1 response', 'url': 'https://www.example.com/aaa'}, {'title': 'bbb', 'responses': '4 responses', 'url': 'https://www.example.com/bbb'}, {'title': 'ccc', 'responses': '2 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'ddd', 'responses': '8 responses', 'url': 'https://www.example.com/ccc'}, {'title': 'eee', 'responses': '2 responses', 'url': 'https://www.example.com/eee'}]
res = [item['url'] for item in data if int(item['responses'].split()[0]) < 2]
print(res)  # --> ['https://www.example.com/aaa']

Answer 3

循环遍历列表，并将“responses”键的每个值转换为一个int，然后检查它是否小于2，如果是，则打印URL（插入一个额外的项目，fffin l为清楚起见）：

l = [{'title': 'aaa',
      'responses': '1 response',
      'url': 'https://www.example.com/aaa'
      },
     {'title': 'bbb', 'responses': '4 responses', 'url': 'https://www.example.com/bbb'},
     {'title': 'ccc', 'responses': '2 responses', 'url': 'https://www.example.com/ccc'},
     {'title': 'ddd', 'responses': '8 responses', 'url': 'https://www.example.com/ccc'},
     {'title': 'eee', 'responses': '2 responses', 'url': 'https://www.example.com/eee'},
     {'title': 'fff', 'responses': '1 responses', 'url': 'https://www.example.com/fff'}
 ]


def less_responses_than_n(r, n=2, count=0):
    for d in l:
        if int(d["responses"].split()[0]) < n:
            count += 1
            r[f'url_{count}'] = d["url"]
    return r


r = dict()
print(less_responses_than_n(r))
print(less_responses_than_n(r, n=3))

返回：

{'url_1': 'https://www.example.com/aaa', 'url_2': 'https://www.example.com/fff'}
{'url_1': 'https://www.example.com/aaa', 'url_2': 'https://www.example.com/ccc', 'url_3': 'https://www.example.com/eee', 'url_4': 'https://www.example.com/fff'}