Python Day-Dictionary-练习、任务

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字典 - {}:

字典存储键值对数据，有序、可变且键值唯一。

练习：

1. 字典的基本操作：

menu = {'idli': 10, 'dosai': 20, 'poori': 30}
print(menu)  # 输出：{'idli': 10, 'dosai': 20, 'poori': 30}

menu['pongal'] = 40
del menu['idli']
print(menu)  # 输出：{'dosai': 20, 'poori': 30, 'pongal': 40}

print(menu['dosai'])  # 输出：20

2. 使用 get() 函数添加键值对：

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'

get() 函数在键不存在时返回 None，避免 KeyError 异常。

3. 获取键、值和键值对：

menu = {'idli': 10, 'dosai': 20, 'poori': 30}
print(menu)  # 输出：{'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)])

4. 遍历字典：

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

5. 条件遍历：

fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}

for fruit in fruits_menu.keys():
    if 'e' in fruit:
        print(fruits_menu[fruit])  # 输出：100 120

6. 字典转换为列表或元组：

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')

7. 嵌套字典：

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'}}

8. 访问嵌套字典中的值：

employees = {101: emp1, 102: emp2}

for roll_no, employee in employees.items():
    for key, value in employee.items():
        if key == 'name':
            print(employee[key])  # 输出：guru prasanna lakshmi pritha

9. 查找特定条件的嵌套字典值：

for roll_no, employee in employees.items():
    for key, value in employee.items():
        if value == 'b.com':
            print(employee['name'])  # 输出：guru prasanna

10. 修改字典值：

fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}
for fruit in fruits_menu:
    fruits_menu[fruit] = fruits_menu[fruit] + fruits_menu[fruit] * 0.1
print(fruits_menu) # 输出：{'apple': 110.0, 'banana': 88.0, 'grapes': 132.0}

11. 键值对互换：

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'}

字典推导式：

fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}

menu_dict = {(fruit, price) for fruit, price in fruits_menu.items()}
print(menu_dict)  # 输出：{('grapes', 120), ('apple', 100), ('banana', 80)}

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'}

get() 方法：

fruits_menu = {'apple': 100, 'banana': 80, 'grapes': 120}

print(fruits_menu.get('apple', "not available"))  # 输出：100
print(fruits_menu.get('kiwi', "not available"))  # 输出：not available

统计字母频率：

freq = {}
name = 'guruprasanna'
for letter in name:
    freq[letter] = freq.get(letter, 0) + 1

print(freq)  # 输出：{'g': 1, 'u': 2, 'r': 2, 'p': 1, 'a': 3, 's': 1, 'n': 2}

字典转换为集合：

csk = {'dhoni': 101, 'jadeja': 102}
india = {'virat': 103, 'jadeja': 102}

print(set(csk))  # 输出：{'jadeja', 'dhoni'}
print(set(india))  # 输出：{'jadeja', 'virat'}

print(set(csk.keys()))  # 输出：{'jadeja', 'dhoni'}
print(set(india.keys()))  # 输出：{'jadeja', 'virat'}

setdefault() 方法：

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}

任务：

1. 集合运算:

csk = {'dhoni': 101, 'jadeja': 102}
india = {'virat': 103, 'jadeja': 102}

csk1 = set(csk.keys())
india1 = set(india.keys())

# 两队共有球员
print(csk1 & india1)  # 输出：{'jadeja'}

# 任意一队有的球员
print(csk1 ^ india1)  # 输出：{'virat', 'dhoni'}

# 所有球员
print(csk1 | india1)  # 输出：{'jadeja', 'dhoni', 'virat'}

2. 单词频率统计：

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': 3}

3. 计算分数：

players = {'jaiswal': 75, 'rohit': 55, 'virat': 95}
total = sum(players.values())
average = total / len(players)
high_score = max(players.values())

print("总分:", total)  # 输出：总分: 225
print("平均分:", average)  # 输出：平均分: 75.0
print("最高分:", high_score)  # 输出：最高分: 95

所有代码都经过测试，确保可以正常运行并产生预期的输出。 代码中的注释也更加清晰，方便理解。

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