Question

要声明一个空字典，我要做：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" 
          content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />

    <title>Mini App</title>

    <style>
      body {
        background:white;
      }
      div.user-photo {
        margin: 1em auto;
        width: 150px;
        height: 150px;
        border-radius: 50%;
        overflow: hidden;
      }
      .select {
        margin-bottom: 2.5em;
      }
      .details {
        color: white;
        background-color: #6200ee;
        font-size: 1.3em;
        margin-top: 4em;
        padding: 0.5em 1em;
        border-radius: 10px;
      }
      .details p {
        margin: 0.3em
      }
      #outcome {
        position: 2.2em;
        bottom: 6.5em;
        width: 100px;
        text-align: center;
      }
      #outcome h3 {
        padding: 1em;
        background-color: white;
        border-radius: 10%;
        margin: 0;
      }
      #outcome p {
        height: 40px;
        color: white;
        border-bottom: 5px solid white;
        font-size: 2em;
        margin: 0;
        padding: 0.5em 0;
      }
      #oracle {
        margin-top: 2.5em;
        border: 1px solid #333;
        width: 100%;
      }
    </style>
  </head>
  <body>
    <button class="mdc-icon-button materials-icons" id="filter-query">
      filter_list
    </button>
    <div class="select">
      <select class="select-text" id="select-text">
        <option selected disabled value="0">Select user</option>
      </select>
    </div>
    <div class="user-photo">
      <img
           src="https://via.placeholder.com/150

 C/O https://placeholder.com/"
           alt="user-photo"
           />
    </div>
    <div class="details mdc-elevation--z3">
      <p>
        <span class="prop" data-age="Age:">Age</span
          ><span class="value" data-age-value="">&nbsp;: 40</span>
      </p>
      <p>
        <span class="prop" data-height="Height:">Height</span
          ><span class="value" data-height-value="">&nbsp;: 6</span>
      </p>
      <p>
        <span class="prop" data-weight="Weight:">Weight</span
          ><span class="value" data-weight-value="">&nbsp;: 75</span>
        </p>
      <p>
        <span class="prop" data-gender="Gender:">Gender</span
          ><span class="value" data-gender-value="">&nbsp;: Male</span>
      </p>
      <p>
        <span class="prop" data-country="Counry:">Country</span
          ><span class="value" data-country-value="">&nbsp;: Nigeria</span>
      </p>
    </div>
    <button id="oracle" class="mdc-button">
      Calculate BMI
      </button>
    <div id="outcome">
      <h3 class="mdc-typography--headline5">BMI</h3>
      <p></p>
    </div>
    <script>
      const fetchAndDisplayUsers = () => {
        users.push({
          age: 40,
          weight: 75,
          height: 6,
          country: 'Nigeria',
          name: 'Charles Odili',
          id: 'dfhb454768DghtF'
        });

        displayUsers(users);
      };

      const startApp = () => {

      };

      startApp();
    </script>
  </body>
</html>

要声明一个空字典的空字典，我也可以这样做：

mydict = dict()

然后在需要时添加字典：

mydictofdict = dict()

以及需要的元素：

mydict1 = dict()
mydictofdict.update({1:mydict1})

它是pythonic吗？有更好的执行方法吗？

Answer 1

您可以将collections.defaultdict用于嵌套字典，在其中定义字典的初始值

from collections import defaultdict

#Use the initial value as a dictionary
dct = defaultdict(dict)

dct['a']['b'] = 'c'
dct['d']['e'] = 'f'

print(dct)

输出将为

defaultdict(<class 'dict'>, {'a': {'b': 'c'}, 'd': {'e': 'f'}})

Answer 2

您可以使用a创建空字典：

{}

您可以像第一个那样创建dict（作为值）dict：

d = {}

您可以通过d = { 1: {}, 2: {} }来修改字典的值：

[]

d = {1: 0} d[1] = 1 d

与dict中的dict类似：

{1: 1}

d = { 1: {}, 2: {} } d[1][4] = 5 d

如果要根据键列表创建字典，则可以使用字典推导：

{1: {4: 5}, 2: {}}

keys = [1,2,3,4,5] d = {key: {} for key in keys} d

如何在Python 2.7中声明一个空字典的空字典？

2 个答案: