字典-{}：

-->將數(shù)據(jù)值存儲(chǔ)在鍵：值對
中 -->有序、可更改且不允許重復(fù)。

練習(xí)：
1.

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

menu['pongal'] = 40 

del menu['idli']
print(menu)

print(menu['dosai'])

輸出：

{'idli': 10, 'dosai': 20, 'poori': 30}
{'dosai': 20, 'poori': 30, 'pongal': 40}
20

2。要在空字典中添加鍵:值對，使用 get() 函數(shù)

time_table = {}

time_table['tamil'] = 10
time_table['english']= 10

print(time_table)

print(time_table['tamil'])
print(time_table.get('tamil'))
print(time_table.get('maths'))
print(time_table['maths'])

輸出：

{'tamil': 10, 'english': 10}
10
10
None
KeyError: 'maths'

-->如果通常我們輸入字典中沒有的鍵，那么輸出將是 KeyError。
-->相反，如果我們使用 get() 函數(shù)，它不會(huì)返回任何內(nèi)容。

3.獲取鍵、值以及兩者

menu = {'idli':10, 'dosai':20, 'poori':30}
print(menu)
print(menu.keys())
print(menu.values())
print(menu.items())

輸出：

{'idli': 10, 'dosai': 20, 'poori': 30}
dict_keys(['idli', 'dosai', 'poori'])
dict_values([10, 20, 30])
dict_items([('idli', 10), ('dosai', 20), ('poori', 30)])

Keys-->從字典中打印鍵(dict_name.keys())。
值-->打印字典中的值(dict_name.values())。
items-->將字典中的鍵和值打印為元組 (dict_name.items())。

4。從字典中單獨(dú)獲取鍵、值或項(xiàng)目。

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

for fruit in fruits_menu.keys():
    print(fruit)

for price in fruits_menu.values():
    print(price)

for fruit, price in fruits_menu.items():
    print(fruit, price)

輸出：

apple
banana
grapes
100
80
120
apple 100
banana 80
grapes 120

5。如果鍵包含字母“e”，則打印值。

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

for fruit in fruits_menu.keys():
    if 'e' in fruit:
        print(fruits_menu[fruit])

輸出：

100
120

6。將字典轉(zhuǎn)換為元組或列表。

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

print(list(fruits_menu))
print(tuple(fruits_menu))

輸出：

['apple', 'banana', 'grapes']
('apple', 'banana', 'grapes')

7。嵌套字典。

emp1 = {'name':'guru prasanna', 'qual':'B.Com'}
emp2 = {'name':'lakshmi pritha', 'qual': 'M.E'}

print(emp1)
print(emp2)

employees = {101:emp1, 102:emp2}
print(employees)

輸出：

{'name': 'guru prasanna', 'qual': 'B.Com'}
{'name': 'lakshmi pritha', 'qual': 'M.E'}
{101: {'name': 'guru prasanna', 'qual': 'B.Com'}, 102: {'name': 'lakshmi pritha', 'qual': 'M.E'}}

8。從字典中單獨(dú)獲取員工姓名。

emp1 = {'name':'guru prasanna', 'qual':'B.Com'}
emp2 = {'name':'lakshmi pritha', 'qual': 'M.E'}


employees = {101:emp1, 102:emp2}
print(employees)

for roll_no, employee in employees.items():
    for key, value in employee.items():
        if key == 'name':
            print(employee[key])

輸出：

{101: {'name': 'guru prasanna', 'qual': 'B.Com'}, 102: {'name': 'lakshmi pritha', 'qual': 'M.E'}}
guru prasanna
lakshmi pritha

9。單獨(dú)獲取 B.com 員工。

emp1 = {'name':'guru prasanna', 'qual':'B.Com'}
emp2 = {'name':'lakshmi pritha', 'qual': 'M.E'}

employees = {101:emp1, 102:emp2}

for roll_no, employee in employees.items():
    for key, value in employee.items():
        if value == 'B.Com':
            print(employee['name'])

輸出：

guru prasanna

10。每個(gè)值增加 10%。

fruits_menu = {'apple':100, 'banana':80, 'grapes':120}
for fruit in fruits_menu.values():
    fruit=fruit+(fruit/10)
    print(fruit)

輸出：

110.0
88.0
132.0

11。轉(zhuǎn)換鍵-->價(jià)值觀與價(jià)值-->鍵。

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

for fruit,price in fruits_menu.items():
    new_menu[price] = fruit

print(new_menu)

輸出：

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

字典理解

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

menu_dict = {(fruit,price) for fruit,price in fruits_menu.items()}
print(menu_dict)

menu_dict = {fruit: price for fruit,price in fruits_menu.items()}
print(menu_dict)

#To reverse key-->value and value-->key

menu_dict = {price : fruit for fruit,price in fruits_menu.items()}
print(menu_dict)

輸出：

{('grapes', 120), ('apple', 100), ('banana', 80)}
{'apple': 100, 'banana': 80, 'grapes': 120}
{100: 'apple', 80: 'banana', 120: 'grapes'}

get()
get() 方法返回具有指定鍵的項(xiàng)的值。
-->如果字典中不存在鍵，則返回?zé)o。

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

print(fruits_menu.get('apple',"not available"))
print(fruits_menu.get('kiwi',"not available"))

輸出：

100
not available

查找給定字符串中字母的頻率

#frequency of each letter in a given string
freq = {}
name = 'guruprasanna'
for letter in name: 
    freq[letter] = freq.get(letter,0)+1

print(freq)

輸出：

{'g': 1, 'u': 2, 'r': 2, 'p': 1, 'a': 3, 's': 1, 'n': 2}

將字典轉(zhuǎn)換為集合

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

print(set(csk))
print(set(india))

print(set(csk.keys()))
print(set(india.keys()))

輸出：

{'dhoni', 'jadeja'}
{'virat', 'jadeja'}
{'dhoni', 'jadeja'}
{'virat', 'jadeja'}

setdefault()

--> setdefault() 方法返回具有指定鍵的項(xiàng)目的值。
-->如果鍵不存在，則插入具有指定值的鍵。

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

csk.setdefault('rohit',100)
print(csk)
csk.setdefault('dhoni',100)
print(csk)

輸出：

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

menu['pongal'] = 40 

del menu['idli']
print(menu)

print(menu['dosai'])

任務(wù)：

1。查找：
a) 兩個(gè)團(tuán)隊(duì)都有共同點(diǎn)
b) 出現(xiàn)在任何一支球隊(duì)
c) 總玩家姓名

{'idli': 10, 'dosai': 20, 'poori': 30}
{'dosai': 20, 'poori': 30, 'pongal': 40}
20

輸出：

time_table = {}

time_table['tamil'] = 10
time_table['english']= 10

print(time_table)

print(time_table['tamil'])
print(time_table.get('tamil'))
print(time_table.get('maths'))
print(time_table['maths'])

2。查找字符串中單詞的出現(xiàn)頻率 - 'a Rose is a Rose is a Rose'。

{'tamil': 10, 'english': 10}
10
10
None
KeyError: 'maths'

輸出：

menu = {'idli':10, 'dosai':20, 'poori':30}
print(menu)
print(menu.keys())
print(menu.values())
print(menu.items())

3。在字典中查找總分、平均分和高分。
玩家 = {'jaiswal':75, 'rohit':55, 'virat':95}

{'idli': 10, 'dosai': 20, 'poori': 30}
dict_keys(['idli', 'dosai', 'poori'])
dict_values([10, 20, 30])
dict_items([('idli', 10), ('dosai', 20), ('poori', 30)])

輸出：

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

for fruit in fruits_menu.keys():
    print(fruit)

for price in fruits_menu.values():
    print(price)

for fruit, price in fruits_menu.items():
    print(fruit, price)

apple
banana
grapes
100
80
120
apple 100
banana 80
grapes 120

輸出：

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

for fruit in fruits_menu.keys():
    if 'e' in fruit:
        print(fruits_menu[fruit])

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