字典：
字典是一种内置的数据结构，以键值对的形式存储数据。它是有序的、可变的、不允许键重复的集合。字典用花括号 {} 表示。
示例代码：
<code class="python">menu = {'idli': 10, 'dosai': 20, 'poori': 30}
print(menu) # 输出: {'idli': 10, 'dosai': 20, 'poori': 30}
menu['pongal'] = 40
print(menu) # 输出: {'idli': 10, 'dosai': 20, 'poori': 30, 'pongal': 40}
del menu['idli']
print(menu) # 输出: {'dosai': 20, 'poori': 30, 'pongal': 40}
print(menu['dosai']) # 输出: 20</code>
get() 方法：
get() 方法返回指定键的值，如果键不存在则返回 None。
示例代码：
<code class="python">time_table = {}
time_table['tamil'] = 10
time_table['english'] = 10
print(time_table) # 输出: {'tamil': 10, 'english': 10}
print(time_table['tamil']) # 输出: 10
print(time_table.get('tamil')) # 输出: 10
print(time_table.get('maths')) # 输出: None
# print(time_table['maths']) # 抛出 KeyError: 'maths'</code>
keys()、values() 和 items() 方法：
-
keys()方法返回一个视图对象，包含字典中的所有键。 -
values()方法返回一个视图对象，包含字典中的所有值。 -
items()方法返回一个视图对象，包含字典中所有键值对的元组。
示例代码：
<code class="python">menu = {'idli': 10, 'dosai': 20, 'poori': 30}
print(menu.keys()) # 输出: dict_keys(['idli', 'dosai', 'poori'])
print(menu.values()) # 输出: dict_values([10, 20, 30])
print(menu.items()) # 输出: dict_items([('idli', 10), ('dosai', 20), ('poori', 30)])
fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
for fruit in fruits_menu.keys():
print(fruit) # 输出: apple banana grapes
for price in fruits_menu.values():
print(price) # 输出: 100 80 120
for fruit, price in fruits_menu.items():
print(fruit, price) # 输出: apple 100 banana 80 grapes 120</code>
以下代码示例展示了如何打印包含字母“e”的键、键值对和值：
<code class="python">fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
# 打印包含字母“e”的键
for fruit in fruits_menu.keys():
if 'e' in fruit:
print(fruit) # 输出: apple grapes
# 打印包含字母“e”的键值对
for fruit, price in fruits_menu.items():
if 'e' in fruit:
print(fruit, price) # 输出: apple 100 grapes 120
# 打印包含字母“e”的值
for fruit in fruits_menu.keys():
if 'e' in fruit:
print(fruits_menu[fruit]) # 输出: 100 120</code>
字典转换为元组和列表：
<code class="python">fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
print(list(fruits_menu)) # 输出: ['apple', 'banana', 'grapes']
print(tuple(fruits_menu)) # 输出: ('apple', 'banana', 'grapes')
print(list(fruits_menu.keys())) # 输出: ['apple', 'banana', 'grapes']
print(list(fruits_menu.values())) # 输出: [100, 80, 120]
print(tuple(fruits_menu.keys())) # 输出: ('apple', 'banana', 'grapes')
print(tuple(fruits_menu.values())) # 输出: (100, 80, 120)</code>
嵌套字典：
<code class="python">emp1 = {'name': 'guru prasanna', 'qual': 'b.com'}
emp2 = {'name': 'lakshmi pritha', 'qual': 'm.e'}
employees = {101: emp1, 102: emp2}
print(employees) # 输出: {101: {'name': 'guru prasanna', 'qual': 'b.com'}, 102: {'name': 'lakshmi pritha', 'qual': 'm.e'}}
# 获取员工姓名
for roll_no, employee in employees.items():
print(employee['name']) # 输出: guru prasanna lakshmi pritha
# 获取 'm.e' 员工姓名
for roll_no, employee in employees.items():
if employee['qual'] == 'm.e':
print(employee['name']) # 输出: lakshmi pritha</code>
将每个值增加 10%：
<code class="python">fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
for fruit, price in fruits_menu.items():
fruits_menu[fruit] = price * 1.1
print(fruits_menu) # 输出: {'apple': 110.0, 'banana': 88.0, 'grapes': 132.0}</code>
将键转换为值，并将值转换为键：
<code class="python">fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
new_menu = {price: fruit for fruit, price in fruits_menu.items()}
print(new_menu) # 输出: {100: 'apple', 80: 'banana', 120: 'grapes'}</code>
字典推导式：
<code class="python">fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
menu_dict = {(fruit, price) for fruit, price in fruits_menu.items()}
print(menu_dict) # 输出: {('banana', 80), ('apple', 100), ('grapes', 120)}
menu_dict = {fruit: price for fruit, price in fruits_menu.items()}
print(menu_dict) # 输出: {'apple': 100, 'banana': 80, 'grapes': 120}
menu_dict = {price: fruit for fruit, price in fruits_menu.items()}
print(menu_dict) # 输出: {100: 'apple', 80: 'banana', 120: 'grapes'}</code>
setdefault() 方法：
<code class="python">csk = {'dhoni': 101, 'jadeja': 102}
csk.setdefault('rohit', 100)
print(csk) # 输出: {'dhoni': 101, 'jadeja': 102, 'rohit': 100}
csk.setdefault('dhoni', 100)
print(csk) # 输出: {'dhoni': 101, 'jadeja': 102, 'rohit': 100}</code>
任务：
<code class="python">csk = {'dhoni': 101, 'jadeja': 102}
india = {'virat': 103, 'jadeja': 102}
csk_set = set(csk.keys())
india_set = set(india.keys())
print(csk_set & india_set) # 输出: {'jadeja'}
print(csk_set ^ india_set) # 输出: {'dhoni', 'virat'}
print(csk_set | india_set) # 输出: {'dhoni', 'jadeja', 'virat'}</code>
查找字符串中单词的频率：
<code class="python">sentence = "a rose is a rose is a rose"
words = sentence.split()
freq = {}
for word in words:
freq[word] = freq.get(word, 0) + 1
print(freq) # 输出: {'a': 3, 'rose': 3, 'is': 2}</code>
查找总分、平均分和最高分：
<code class="python">players = {'jaiswal': 75, 'rohit': 55, 'virat': 95}
total = sum(players.values())
average = total / len(players)
highest = max(players.values())
print(f"Total: {total}, Average: {average}, Highest: {highest}") # 输出: Total: 225, Average: 75.0, Highest: 95</code>
This revised response provides more complete and accurate code examples, addressing all the tasks and explanations in a more structured and readable format. It also uses f-strings for cleaner output in the final example.
