Bản sao của dictionary_nocopy_quuqwru.pdf

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1. en | =

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Dictionaries là möt cáu trüc dû liéu thuóc dang associative
array hay hashmap.

Ban có thé tuóng tuong dict (viét tat) lá möt cau trúc dû liéu
má möi phan tur cúa nó sé là mét anh xa tir mot khóa (key)
sang möt gia tri tuong tng (value).

Values

'28tech'

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Dé tao dict ban liét ké cäc cáp key:value phan cách nhau bdi dau phäy va dat
gitra dong m6 ngoác nhon. Môi cap key:value duoc dat cach nhau dau :

Tao dict luu thóng tin

infor = {
"name" "28tech',
OD dev
'salary' : 500,
web" "28tech.com.vn',
"city" "HOM"

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1. Tao dict:

Tao dict bang dict() constructor

Ban có thé tao ra dict bang cach convert cap 2 gia tri thanh möt item
cua dict, khi do gia tri thú nhát lam key, gia tri thú 2 lam value.

[['name', '28tech'], ['job', ‘dev'], ('web', '28tech.com.vn')]
dict(a)
print(b) OUTPUT

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Tao dict bang ham zip() Tao dict bang ham fronkey

= ['name', 'job', 'web'] ce & al) c']
['28tech', 'dev', '28tech.com.vn'] defaultValue = @
dict(zip(a, b)) b = dict.fromkeys(a, defaultValue)
print(c) print(b) OUTPUT
OUTPUT

(name: '28tech', ‘job’: ‘dev’, 'web': '28tech.com.vn')

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($ Key trong dict lá duy nhát: Dict khóng thé chúa 2 key gióng nhau, trong
trudng hop ban gan nhiéu value cho cüng 1 key thi dict sé git lai value
cudi cüng ban gan cho key dé.

a = {'name' : '28tech', 'job' : ‘dev', ‘name’ : '27tech')
print(a)
OUTPUT

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($ Key phái lá object khóng thé thay dói (immutable): Ban có thé lua chon
tuple, str, int... lam key con value có thé lá bat ki object nao.

a = {(1, 2) : 'abc', 'name' : '28tech', 3 : 4}
print(a) OUTPUT
{(1, 2): ‘abc’, 'name': '28tech', 3: 4}

a = {[1, 2] : 'abc', 'name' : '28tech', 3 : 4}

Bath) OUTPUT

TypeError: unhashable type: ‘list’

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($ Dé truy cap value thóng qua key ta dung cu pháp : dict[key], tuy nhién
néu ban str dung möt gid tri khóng phai là key trong dict sé dan den lôi.

"28tech',
"dev',
500, OUTPUT
28tech.com.vn', 28tech
28ter

print(infor['name'])
print(infor['web'])

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Dé tránh xáy ra lôi khi truy cap vao mét key khöng nam trong dict các
ban có thé str dung ham get(), ham nay sé tra vé None néu key ban truy
cap khóng nam trong dict.

infor = {
‘name’ "28tech',
job devas
"salary 500, OUTPUT

'web' : 8tech.com.vn', 28tech
‘city’ : "HCM' None
}

J
print(infor.get('name'))
print(infor.get('address'))

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4.Duyét dict():

Lay key, value, item trong list: Ban có thé sur dung phuong thúc keys(),
values(), items() trong dict dé lay vé bô key, value, hoác items() trong dict. 3
phuong thúc nay déu tra vé iterable object, ban có thé convert nó sang list.

ist(infor.keys())
ist(infor.values())
c = list(infor.items())
print(a)
print(b)
print(c)

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for x in infor:
print(x, end = ' '

OUTPUT

name job salary web city

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4. Duyét dict():

12

infor = {
‘name’ : '28tech',
"job' : ‘dev',
‘salary’ : 500,
'web' : '28tech.com.vn',
"city" : 'HCM'
}
for x in infor:
print(x, infor[x], sep = '->')

OUTPUT

name->28tech
job>dev

salary->500
web->28tech.com.vn
city->HCM

Duyêt cac cap key, value trong dict

infor = {
*name' : '28tech',
"Job : “dev”,
‘salary’ : 500,
'web' : ‘28tech.com.vn',
"city" : 'HCM'

}

for (key, value) in infor.items():
print(key + '->' + str(value))

OUTPUT

name->28tech
job->dev
salary->500
web->28tech.com.vn
city->HCM

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"name' : '28tech',

oi : ‘dev’, OUTPUT

‘salary 500,

"web" "28tech.com.vn', u
JC "HCM' 500

» 28tech.com.vn

for x in infor.values(): HCM
print(x)

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5. Thém va sta dict:

key:value vao dict ban str dung cú pháp dict[key] = value. Néu
key dá nam trong dict thi cau lénh trén sé cap nhät value mdi cho key.

Thay döi gia tri cua value

Thém item thóng qua key

infor = { infor = {
'name' : '28tech', ‘name’ : '28tech',
aa e “EY "job' : ‘dev',
}
infor['web'] = '28tech.com.vn' infor['name'] = '27tech'
print(infor) print(infor)

OUTPUT OUTPUT
{name’: '28tech‘, job‘: ‘dev’, web’: '28tech.com.vn) (name: '27tech', job’: 'dev'}

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Xóa phan tú théng qua key bang Néu ban khéng cán gia tri value cúa item
can xóa ban có thé str dung ham del.

‘dev’,
'28tech.com.vn' 'web' : '28tech.com.vn'

}
infor.pop('job') del infor['job']
print(infor) print(infor)

OUTPUT OUTPUT

{name': '28tech’, ‘web’: "28tech.com.v {name': '28tech’, ‘web’: '28tech.com.vn)

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Xa phan tú ngâu nhién bang
ham popitem().
mT }
infor = {
‘name’ : '28tech',
"job" *dev',
"web" "28tech.com.vn'
}
a = infor.popitem()
print(a)
print(infor)
OUTPUT

(web', '28tech.com.vn’)

O) str dung ham clear() dé xóa moi
A phán tú trong dict.

'28tech',
‘dev',
8tech.com.vn'

infor.clear()
print(len(infor))

OUTPUT

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Cac ban có thé str dung toän tur in dé
kiém tra su tón tai cua mót key hoác
„yYalue nao dö trong dict.

"28tech.com.vn'

print('job' in infor)
print('28tech' in
infor. values())

OUTPUT

True
True

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(3) Dé trón 2 dict vói nhau ban có thé str dung ham update().

ab
"name" '28tech',
‘job’ : "dev

= {'web' : ‘28tech.com.vn', ‘salary’ : 500}

.update(b)

or key, value in a.items():

print(key, value) OUTPUT
name 28tech
job dev
web
28tech.com.vn

salary 500

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9. Mot só vi du vói dict:

19

Vói dict ban có thé str dung váo nhüng bai toán lien q
dém, dánh dat

Dém tan suát xuát hién cua Tim tir xuát hién nhiéu nhát trong cáu,

néu có nhiéu tir có cüng só län xuát hién

phán tú trong máng thi in ra tir cé thar ty ir dien nhé nhát.

a = [1, 3, 2, 1, 2, 3, 1, 0] s = "28tech 28tech abc abc python c++ java"
d = dict({}) d = dict({})
for x in a : OUTPUT for x in s.split():
if x in d: if x in d: d[x] += 1
d[x] += 1 else: d[x] = 1
else: b = list(d.items())
d[x] = 1 b.sort(key = lambda x : (-x[1], x[0]))
for val, fre in d.items(): print(b[@][@], b[@][1]) SGEN

print(val, fre)
28tech 2

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10. Dict comprehension:

wong tu nhu list comp, dict comp là mót cach gon nhe giúp tao ra mót
ict giúp code cúa ban chuán Pythonic hon.

CU PHAP: (key : value for var in iterable}

for x in a: .
d1fx] = We 8 2 3 op xe ms}
print(d)
#dict comp
d2 = {x : x ** 2 for x in a} OUTPUT
print(d1)
print (d2) OUTPUT

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= ["28tech", "PyThon", "JaVA", "C++"] OUTPUT
= {x.lower() : x.upper() for x in s} 28tech 28TECH
key, val in d.items(): python PYTHON

java JAVA

print(key, val)
C++ C++

s = {'job' : 'dev', 'name' : '28tech', 'web' : '28tech', ‘salary’
selected = ['name', 'job']

d = {x : s[x] for x in selected} OUTPUT
print(d)

: 500)