To’plamlar haqida ma’lumot. II. Asosiy qism

defaultdict dictdan qanday farq qiladi

Agar siz lug'atda mavjud bo'lmagan kalitga kirishga harakat qilsangiz, u KeyError. Holbuki, a defaultdictda u ni bermaydi KeyError.
Bu kalit xatosini bermaydi. Agar mavjud bo'lmagan kalitga kirsangiz, defaultdictu standart qiymatni qaytaradi.
Sintaksis:defaultdict(default_factory)
Biz mavjud bo'lmagan kalitga kirganimizda, default_factoryfunktsiya standart qiymatni qaytaradi
# Creating a defaultdict and trying to access a key that is not present.
from collections import defaultdict
def_dict = defaultdict(object)
def_dict['fruit'] = 'orange'
def_dict['drink'] = 'pepsi'
print(def_dict['chocolate'])

#> <object object at 0x7f591a2f4510>

Yuqoridagi buyruqni bajarsangiz, u sizga bermaydi KeyError.
Agar siz so'ralgan kalit uchun qiymat mavjud emasligini chiqarmoqchi bo'lsangiz, o'zingizning funksiyangizni belgilashingiz va uni defaultdict-ga o'tkazishingiz mumkin.
Quyidagi misolga qarang
# Passing a function to return default value
def print_default():
return 'value absent'

def_dict=defaultdict(print_default)

print(def_dict['chocolate'])

#> value absent

Boshqa barcha yo'llar bilan u oddiy lug'at bilan bir xil. Xuddi shu sintaksis buyruqlari defaultdict uchun ham ishlatiladi.
Aslida, usul KeyErroryordamida lug'atni engib o'tish mumkin.get
# Make dict return a default value
mydict = {'a': 'Apple', 'b': 'Ball'}
mydict.get('c', 'NOT PRESENT')

#> 'NOT PRESENT'

OrderedDict

Dict - bu kalit qiymat juftlarining TARTIB ETMAGAN to'plami. Biroq, OrderedDictkalitlar kiritilgan TARTIBIni saqlaydi.
ning kichik sinfidir dict.
Men oddiy yaratmoqchiman dictva uni OrderedDictsizga farqni ko'rsatish uchun qilaman
# create a dict and print items
vehicle = {'bicycle': 'hercules', 'car': 'Maruti', 'bike': ' Harley', 'scooter': 'bajaj'}

print('This is normal dict')

for key,value in vehicle.items():
print(key,value)

print('-------------------------------')

# Create an OrderedDict and print items

from collections import OrderedDict
ordered_vehicle=OrderedDict()
ordered_vehicle['bicycle']='hercules'
ordered_vehicle['car']='Maruti'
ordered_vehicle['bike']='Harley'
print('This is an ordered dict')

for key,value in ordered_vehicle.items():

print(key,value)

#> This is normal dict

#> bicycle hercules
#> car Maruti
#> bike Harley
#> scooter bajaj
-------------------------------
#> This is an ordered dict
#> bicycle hercules
#> car Maruti
#> bike Harley
In OrderedDict, hatto ba'zi kalitlarning qiymatini o'zgartirgandan keyin ham, tartib bir xil yoki o'zgarishsiz qoladi.
# I have changed the value of car in this ordered dictionary.
ordered_vehicle['car']='BMW'# I have changed the value of car in this ordered dictionary.
for key,value in ordered_vehicle.items():
print(key,value)

#> bicycle hercules

#> car BMW
#> bike harley davison