Python 缺少 self 参数

Question

您好 :> 我正在学习 python 对象编程。我做了简单的代码：

import random
drawn = []
class Lottery():
    def __init__(self, letter, drawn):
        self.letters = ['a', 'b', 'c', 'd', 'f', 'g', 'h']
        self.letter = letter
        self.drawn = drawn

    def drawnumbers():
        number = random.randint(0, 10)
        return number
    def drawletters(self):
        letter = random.choice(self.letters)
        return letter()

    for i in range(0,9):
        drawn.append(drawnumbers())
    for i in range(0,3):
        drawn.append(drawletters())
    print(drawn)

这是错误：

Traceback (most recent call last):
  File "C:/Users/pawee/PycharmProjects/pythonProject1/lottery.py", line 3, in <module>
    class Lottery():
  File "C:/Users/pawee/PycharmProjects/pythonProject1/lottery.py", line 19, in Lottery
    drawn.append(drawletters())
TypeError: drawletters() missing 1 required positional argument: 'self'

我做错了什么？

Answer 1

因此，当您定义属于 class 的方法时，它们都将 'self' 作为第一个参数。

定义 class 时也不要包含括号，除非它继承自另一个 class

但是，还有一些错误。

我认为这可能是格式错误，但最后几行需要取消缩进，因此它们在 class.

之外

如果它们应该是 class 的一部分，那么您需要将它们放在自己的方法中（也包括 self 参数）。

为了在没有实例的情况下调用彩票 class，它们也必须是静态的。

所以要达到运行需要让您的代码看起来像这样...

import random
drawn=[]
class Lottery: #no parenthesis
    def __init__(self, letter, drawn):
        self.letters = ['a', 'b', 'c', 'd', 'f', 'g', 'h']
        self.letter = letter
        self.drawn = drawn
    
    @staticmethod
    def drawnumbers(self): #include self
        number = random.randint(0, 10)
        return number

    @staticmethod
    def drawletters(self): #include self
        letter = random.choice(self.letters)
        return letter #no parenthesis

#unindent so we aren't in the class anymore
for i in range(0,9):
    drawn.append(Lottery.drawnumbers())
for i in range(0,3):
    drawn.append(Lottery.drawletters())
print(drawn) 
#at this point, drawn is not associated with the lottery class
# to associate it, you need to make a variable out of the class
lotteryObj = Lottery("A", drawn) #it takes 2 arguments, letter and drawn
print(lotteryObj.drawn) #=> [...]
print(lotteryObj.letter) #=> "A"

然而，这并不是 classes 应该如何工作。

如果你想做彩票class，最好让class保存它使用的数据，并有影响该数据的方法。

这是默认参数派上用场的地方。它们允许您为 class 定义不需要给出的参数。

通过这种方式，您可以获得一些中奖号码的列表，将其提供给您的彩票 class，然后将其添加到列表中，再抽取 numbers/letters 个。

import random
drawn=[]
class Lottery: #no parenthesis
    def __init__(self, drawn=[]): #default for drawn, letter not needed
        self.letters = ['a', 'b', 'c', 'd', 'f', 'g', 'h']
        self.drawn = drawn #if you don't give the class a list, it makes an empty list

    def drawnumbers(self): #include self
        number = random.randint(0, 10)
        #instead of returning, change the list this class has using self
        self.drawn.append(number)

    def drawletters(self): #include self
        letter = random.choice(self.letters)
        self.drawn.append(letter)
    #you can add a print method or get methods for printing or getting the drawn list

#unindent so we aren't in the class anymore
lotto1 = Lottery()
lotto2 = Lottery([1]) #give it a list with something in it
for i in range(0,9):
    lotto1.drawnumbers()
    lotto2.drawnumbers()
for i in range(0,3):
    lotto1.drawletters()
    lotto2.drawletters()
print(lotto1.drawn)
print(lotto2.drawn)

Python 缺少 self 参数

Python is missing self argument

python

class

object