如何在类函数之间传递变量？

Question

好吧，我需要获取price变量以传递给Tela 4函数whatever。我对Python还是很陌生，我也不知道该怎么做，即使我以为它很简单

这是当前代码的外观，随时可以添加有关改进代码的建议。

class Tela2(Screen):
    def op_dimoff(self):
        self.price = float((int(self.ngd) * 0.87 * 1.75) + self.price_inv)

class Tela4 (Screen):
    def whatever(self):
        tela_two = Tela2
        self.cost_output.text = str(tela_two.price)

“ cost_output”是指奇异果标签

---

更新：

我认为@slackmart的做法是正确的，但仍然无法获得想要的结果。我收到错误AttributeError: 'Tela2' object has no attribute 'irrad'（很抱歉，我没有发布更完整的代码版本，这是我的第一个问题，我害怕发布一个较长的问题）

如果您能帮助我找出解决方案，那么代码现在就是这样：

class Tela2(Screen):

   ngd = ObjectProperty()

   def __init__(self, **kwargs):
       super(Tela2, self).__init__(**kwargs)
       self.price = 0.0
       self.ngd = 0.0
       self.price_inv = 0.0


   def region_define(self, text):

       self.inorte: float = 4.825
       self.inordeste: float = 5.483
       self.icentro: float = 5.082
       self.isudeste: float = 4.951
       self.isul: float = 4.444

       self.kwh_norte: float = 0.871
       self.kwh_nordeste: float = 0.308
       self.kwh_centro: float = 0.290
       self.kwh_sudeste: float = 0.322
       self.kwh_sul: float = 0.320

       if text == 'Norte':
           self.irrad = self.inorte
           self.kwh = self.kwh_norte

       elif text == 'Nordeste':
           self.irrad = self.inordeste
           self.kwh = self.kwh_nordeste

       elif text == 'Centro-Oeste':
           self.irrad = self.icentro
           self.kwh = self.kwh_centro

       elif text == 'Sudeste':
           self.irrad = self.isudeste
           self.kwh = self.kwh_sudeste

       else:
           self.irrad = self.isul
           self.kwh = self.kwh_sul

   def op_dimoff(self):

   # cálculo da Geração Mínima = (NGD/irrad)
   self.gmin = float(self.ngd/self.irrad)# em W/h

   # dimensionamento potência do inversor
   self.pot_seg = self.gmin * 1.3
   self.inv = (600, 1000, 1500, 2000, 3000)
   self.pri_inv = (1434, 1852.2, 1924, 2604, 3899)
   self.x = 0
   for self.x in range(0, len(self.inv)):
       if self.pot_seg <= self.inv[int(self.x)]:
           self.pot_inv = self.inv[int(self.x)]
           self.price_inv = self.pri_inv[int(self.x)]
           break
       else:
           self.x += 1

    self.price = float((int(self.ngd) * 0.87 * 1.75) + self.price_inv)

注意：

  

region_define是kivy旋转器的on_text功能

Answer 1

解决方案

解决方案有两个选择。

注意：

不建议使用tela_two = Tela2()，因为您正在创建对象Tela2的另一个实例，该实例没有与之关联的视图以及属性的不同更新值。

选项1-使用get_screen（）

在此选项中，我们使用get_screen()函数检索实例化的对象Tela2:，以便我们可以访问其方法或属性，例如price。我们将进行以下增强：

kv文件：

• 我们name屏幕name: 'Tela2'和name: 'Tela4'分别用于实例化对象Tela2:和Tela4:。

摘要-kv文件

ScreenManager:
    Tela2:
        name: 'Tela2'
    ...
    Tela4:
        name: 'Tela4'

Py文件

• 使用get_screen()函数检索实例化对象Tela2

摘要-Py文件

def whatever(self):
    tela_two = self.manager.get_screen('Tela2')
    self.cost_output.text = str(tela_two.price)

或

def whatever(self):
    self.cost_output.text = str(self.manager.get_screen('Tela2').price)

选项2-使用ID：tela2

在此选项中，我们将id: tela2添加到实例化对象Tela2:中，并使用ids.tela2访问其方法或属性，例如price。我们将进行以下增强：

kv文件：

• 将id: tela2添加到实例化对象Tela2:

摘要-kv文件

ScreenManager:
    Tela2:
        id: tela2
    ...
    Tela4:

Py文件

• 将tela_two = Tela2替换为tela_two = self.manager.ids.tela2

摘要-Py文件

def whatever(self):
    tela_two = self.manager.ids.tela2
    self.cost_output.text = str(tela_two.price)

或

def whatever(self):
    self.cost_output.text = str(self.manager.ids.tela2.price)

Kivy ScreenManager » default property manager

  

每个屏幕默认都有一个属性manager，该属性为您提供   的ScreenManager的实例。

示例-使用ID：tela2

以下示例说明了如何使用get_screen()函数和ids.tela2访问对象Tela2中定义的属性。它还通过调用on_text和self.region_define('Norte')模拟self.op_dimoff()事件。

main.py

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.properties import ObjectProperty
from kivy.lang import Builder

Builder.load_string("""
<ScreenManagement>:
    Tela2:
        id: tela2
        name: 'Tela2'
    Tela4:
        name: 'Tela4'

<Tela2>:
    Button:
        text: 'Goto Tela4'
        on_release: root.manager.current = 'Tela4'
<Tela4>:
    on_pre_enter:
        self.whatever()
    Label:
        id: cost_output
        font_size: sp(50)
""")


class Tela2(Screen):
    ngd = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(Tela2, self).__init__(**kwargs)
        self.price = 0.0
        self.ngd = 0.0
        self.price_inv = 0.0

        # simulation
        self.region_define('Norte')
        self.op_dimoff()

    def region_define(self, text):
        self.inorte: float = 4.825
        self.inordeste: float = 5.483
        self.icentro: float = 5.082
        self.isudeste: float = 4.951
        self.isul: float = 4.444

        self.kwh_norte: float = 0.871
        self.kwh_nordeste: float = 0.308
        self.kwh_centro: float = 0.290
        self.kwh_sudeste: float = 0.322
        self.kwh_sul: float = 0.320

        if text == 'Norte':
            self.irrad = self.inorte
            self.kwh = self.kwh_norte

        elif text == 'Nordeste':
            self.irrad = self.inordeste
            self.kwh = self.kwh_nordeste

        elif text == 'Centro-Oeste':
            self.irrad = self.icentro
            self.kwh = self.kwh_centro

        elif text == 'Sudeste':
            self.irrad = self.isudeste
            self.kwh = self.kwh_sudeste

        else:
            self.irrad = self.isul
            self.kwh = self.kwh_sul

    def op_dimoff(self):
        # cálculo da Geração Mínima = (NGD/irrad)
        self.gmin = float(self.ngd / self.irrad)  # em W/h

        # dimensionamento potência do inversor
        self.pot_seg = self.gmin * 1.3
        self.inv = (600, 1000, 1500, 2000, 3000)
        self.pri_inv = (1434, 1852.2, 1924, 2604, 3899)
        self.x = 0
        for self.x in range(0, len(self.inv)):
            if self.pot_seg <= self.inv[int(self.x)]:
                self.pot_inv = self.inv[int(self.x)]
                self.price_inv = self.pri_inv[int(self.x)]
                break
            else:
                self.x += 1

        self.price = float((int(self.ngd) * 0.87 * 1.75) + self.price_inv)


class Tela4(Screen):

    def whatever(self):
        # Each screen has by default a roperty manager that gives you the instance of the ScreenManager used.
        self.ids.cost_output.text = str(self.manager.ids.tela2.price)
        print(f"tela2.irrad={self.manager.ids.tela2.irrad}")
        print(f"tela2.kwh={self.manager.get_screen('Tela2').kwh}")


class ScreenManagement(ScreenManager):
    pass


class TestApp(App):

    def build(self):
        return ScreenManagement()


if __name__ == "__main__":
    TestApp().run()

输出