如何按日期對物件和屬性進行排序？-有解無憂

我有下一個代碼：

class Petshop():
    def __init__(self, entryDate, name, ownerName):
        self.entryDate = entryDate
        self.name = name
        self.ownerName = ownerName

class Pets():
    def __init__(self):
        self.petsList = []
    
    def addPets(self, entryDate, name, ownerName):
        entry_pet = Petshop(entryDate, name, ownerName)
        self.petsList.append(entry_pet)
    
    def printPets(self):
        for pet in self.petsList:
            if pet.entryDate == pet.entryDate:#Here I try to sort by date
                print("---------------",pet.entryDate,'------------------')
                print("Name:", pet.name)
                print("Owner name:", pet.ownerName)

pet = Pets()

pet.addPets('04/13/2021','Pinky', 'David Smith')
pet.addPets('07/10/2020', 'Charlie', 'Joe Davis')
pet.addPets('12/22/2018', 'Teddy', 'Carl Johnson')
pet.addPets('07/10/2020', 'Kenny', 'Susan Jones')
pet.addPets('04/13/2021','Max', 'Bryan Miller')
pet.addPets('07/10/2020', 'Buddy', 'Kathy Brown')
pet.printPets()

使用該代碼，我想按日期對寵物條目進行排序，因此例如我希望列印下一個：

--------------- 04/13/2021 ------------------
Name: Pinky
Owner name: David Smith
Name: Max
Owner name: Bryan Miller
--------------- 07/10/2020 ------------------
Name: Charlie
Owner name: Joe Davis
Name: Kenny
Owner name: Susan Jones
Name: Buddy
Owner name: Kathy Brown
--------------- 12/22/2018 ------------------
Name: Teddy
Owner name: Carl Johnson

但不是這樣，我可以列印每個物件，這不是我所期望的：

--------------- 04/13/2021 ------------------
Name: Pinky
Owner name: David Smith
--------------- 07/10/2020 ------------------
Name: Charlie
Owner name: Joe Davis
--------------- 12/22/2018 ------------------
Name: Teddy
Owner name: Carl Johnson
--------------- 07/10/2020 ------------------
Name: Kenny
Owner name: Susan Jones
--------------- 04/13/2021 ------------------
Name: Max
Owner name: Bryan Miller
--------------- 07/10/2020 ------------------
Name: Buddy
Owner name: Kathy Brown

我試圖在中進行某種排序printPets()，但它不起作用。所以我來這里尋求幫助。謝謝！

uj5u.com熱心網友回復：

itertools.groupby 是你要找的：

    def printPets(self):
        self.petsList.sort(key=lambda p: p.entryDate)
        for group in groupby(self.petsList, key=lambda p: p.entryDate):
            ls = list(group)
            print("---------------", ls[0], '------------------')
            for pet in list(ls[1]):
                print("Name:", pet.name)
                print("Owner name:", pet.ownerName)

uj5u.com熱心網友回復：

您可以sorted()與作為引數傳遞的 lambda 函式一起使用key。編輯：這段代碼應該產生你所期望的。即每個不同日期列印一個輸入日期。

    def printPets(self):
      for inputdate in sorted(list(set(i.entryDate for i in self.petsList))):
          print("---------------",inputdate,'------------------')
          for pet in list(filter(lambda x: x.entryDate == inputdate, self.petsList)):
            print("Name:", pet.name)
            print("Owner name:", pet.ownerName)

uj5u.com熱心網友回復：

此代碼if pet.entryDate == pet.entryDate在您的程式中無效，您可以進行以下更改：

entry_data = ""
if entry_data != pet.entryDate:
    ...
entry_data = pet.entryDate

使用函式排序sorted。

class Petshop:
    def __init__(self, entryDate, name, ownerName):
        self.entryDate = entryDate
        self.name = name
        self.ownerName = ownerName


class Pets:
    def __init__(self):
        self.petsList = []

    def addPets(self, entryDate, name, ownerName):
        entry_pet = Petshop(entryDate, name, ownerName)
        self.petsList.append(entry_pet)

    def printPets(self):
        entry_data = ""
        for pet in sorted(self.petsList, key=lambda pet_shop: pet_shop.entryDate):
            if entry_data != pet.entryDate:  # Here I try to sort by date
                print("---------------", pet.entryDate, '------------------')
            print("Name:", pet.name)
            print("Owner name:", pet.ownerName)
            entry_data = pet.entryDate


pet = Pets()

pet.addPets('04/13/2021', 'Pinky', 'David Smith')
pet.addPets('07/10/2020', 'Charlie', 'Joe Davis')
pet.addPets('12/22/2018', 'Teddy', 'Carl Johnson')
pet.addPets('07/10/2020', 'Kenny', 'Susan Jones')
pet.addPets('04/13/2021', 'Max', 'Bryan Miller')
pet.addPets('07/10/2020', 'Buddy', 'Kathy Brown')
pet.printPets()

--------------- 04/13/2021 ------------------
Name: Pinky
Owner name: David Smith
Name: Max
Owner name: Bryan Miller
--------------- 07/10/2020 ------------------
Name: Charlie
Owner name: Joe Davis
Name: Kenny
Owner name: Susan Jones
Name: Buddy
Owner name: Kathy Brown
--------------- 12/22/2018 ------------------
Name: Teddy
Owner name: Carl Johnson

uj5u.com熱心網友回復：

您必須添加自定義比較函式才能按條件排序。考慮這個例子：

from datetime import datetime

class Petshop():
    def __init__(self, entryDate, name, ownerName):
        self.entryDate = entryDate
        self.name = name
        self.ownerName = ownerName
        # create a utc time or custom integer fro fast compare 
        self.cmptime =  int(datetime.strptime(entryDate, "%m/%d/%Y").strftime('%Y%m%d'))
        pass

    def __lt__(self, other):
        return self.cmptime < other.cmptime

    def __eq__(self, other):
        return self.cmptime == other.cmptime


class Pets():
    def __init__(self):
        self.petsList = []

    def addPets(self, entryDate, name, ownerName):
        entry_pet = Petshop(entryDate, name, ownerName)

        self.petsList.append(entry_pet)

    def printPets(self):
        self.petsList.sort()
        for pet in (self.petsList):
            if pet.entryDate == pet.entryDate:  # Here I try to sort by date
                print("---------------", pet.entryDate, '------------------')
                print("Name:", pet.name)
                print("Owner name:", pet.ownerName)


pet = Pets()


pet.addPets('04/13/2021', 'Pinky', 'David Smith')
pet.addPets('07/10/2020', 'Charlie', 'Joe Davis')
pet.addPets('12/22/2018', 'Teddy', 'Carl Johnson')
pet.addPets('07/10/2020', 'Kenny', 'Susan Jones')
pet.addPets('04/13/2021', 'Max', 'Bryan Miller')
pet.addPets('07/10/2020', 'Buddy', 'Kathy Brown')
pet.printPets()

我從日期時間創建了一個簡單的整數，但您可以轉換為 UTC 時間，然后按順序覆寫__lt__和__gt__函式以使sort函式作業。

uj5u.com熱心網友回復：

您可以datetime在創建 petsList 時匯入和比較日期：

from datetime import datetime

def getDateFromStr(date):
    date_list = []
    for i in date.split('/'):
        date_list.append(int(i))
    # date_list = list(map(lambda x: int(x), date.split('/')))
    return datetime(date_list[2], date_list[0], date_list[1]).date()

class Petshop():
    def __init__(self, entryDate, name, ownerName):
        self.entryDate = entryDate
        self.name = name
        self.ownerName = ownerName

class Pets():
    def __init__(self):
        self.petsList = []
    
    def addPets(self, entryDate, name, ownerName):
        entry_pet = Petshop(entryDate, name, ownerName)
        # creating petsList sorted by date already
        if len(self.petsList) == 0:
            self.petsList.append(entry_pet)
        else:
            for i, pet in enumerate(self.petsList):
                if getDateFromStr(pet.entryDate) < getDateFromStr(entryDate):
                    self.petsList.insert(i, entry_pet)
                    break
                elif i == len(self.petsList) - 1:
                    self.petsList.append(entry_pet)
                    break
    
    def printPets(self):
        for pet in self.petsList:
            if pet.entryDate == pet.entryDate:#Here I try to sort by date
                print("---------------",pet.entryDate,'------------------')
                print("Name:", pet.name)
                print("Owner name:", pet.ownerName)

pet = Pets()

pet.addPets('04/13/2021','Pinky', 'David Smith')
pet.addPets('07/10/2020', 'Charlie', 'Joe Davis')
pet.addPets('12/22/2018', 'Teddy', 'Carl Johnson')
pet.addPets('07/10/2020', 'Kenny', 'Susan Jones')
pet.addPets('04/13/2021','Max', 'Bryan Miller')
pet.addPets('07/10/2020', 'Buddy', 'Kathy Brown')
pet.printPets()

uj5u.com熱心網友回復：

您必須在類中添加魔法方法 __lt__ 才能進行排序。

class Petshop():
    def __init__(self, entryDate, name, ownerName):
        self.entryDate = entryDate
        self.name = name
        self.ownerName = ownerName

    def __lt__(self, other):
        return self.entryDate < other.entryDate


class Pets():
    def __init__(self):
        self.petsList = []

    def addPets(self, entryDate, name, ownerName):
        entry_pet = Petshop(entryDate, name, ownerName)
        self.petsList.append(entry_pet)

    def printPets(self):
        for pet in sorted(self.petsList):
            if pet.entryDate == pet.entryDate:  # Here I try to sort by date
                print("---------------", pet.entryDate, '------------------')
                print("Name:", pet.name)
                print("Owner name:", pet.ownerName)


pet = Pets()

pet.addPets('04/13/2021', 'Pinky', 'David Smith')
pet.addPets('07/10/2020', 'Charlie', 'Joe Davis')
pet.addPets('12/22/2018', 'Teddy', 'Carl Johnson')
pet.addPets('07/10/2020', 'Kenny', 'Susan Jones')
pet.addPets('04/13/2021', 'Max', 'Bryan Miller')
pet.addPets('07/10/2020', 'Buddy', 'Kathy Brown')
pet.printPets()

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標籤：Python 列表排序字典哎呀

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