Python变量不改变

Question

我正在尝试制作一个数据记录代码，供用户输入动物的数量和年龄、出生率以及它们在这一代存活的机会。我尝试过使用return，但是当我运行程序时，变量仍然是0。你知道吗

在这里，我启动了变量

Gen0_J=0
Gen0_A=0
Gen0_S=0
Birth_rate=0
Srate_J=0
Srate_A=0
Srate_S=0
New_generations=5

我的第一个功能

def generation_values():
    Gen0_J=int(input("How many juveniles in Generation 0? "))
    Gen0_A=int(input("How many adults in Generation 0? "))
    Gen0_S=int(input("How many seniles in Generation 0? "))
    Srate_J=float(input("What is the survival rate for juveniles? "))
    Srate_A=float(input("What is the survival rate for adults? "))
    Srate_S=float(input("What is the survival rate for seniles? "))
    Birth_rate=int(input("What is the birth rate? "))
    return Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate

显示变量

def display_values():
    print("\nThe amount of juveniles in Generation 0 is",Gen0_J)
    print("The amount of adults in Generation 0 is",Gen0_A)
    print("The amount of seniles in Generation 0 is",Gen0_S)
    print("The birth rate in Generation 0 is",Birth_rate)
    print("The survival rate for juveniles in Generation 0 is",Srate_J)
    print("The survival rate for adults in Generation 0 is",Srate_A)
    print("The survival rate for seniles in Generation 0 is",Srate_S)

generation_values()
display_values()

但是，变量保持在0

How many juveniles in Generation 0? 5
How many adults in Generation 0? 6
How many seniles in Generation 0? 7
What is the survival rate for juveniles? 0.75
What is the survival rate for adults? 1
What is the survival rate for seniles? 0
What is the birth rate? 2

The amount of juveniles in Generation 0 is 0
The amount of adults in Generation 0 is 0
The amount of seniles in Generation 0 is 0
The birth rate in Generation 0 is 0
The survival rate for juveniles in Generation 0 is 0
The survival rate for adults in Generation 0 is 0
The survival rate for seniles in Generation 0 is 0

Answer 1

变量的范围不一致。你知道吗

你可以这样做：

def generation_values():
    Gen0_J=int(input("How many juveniles in Generation 0? "))
    Gen0_A=int(input("How many adults in Generation 0? "))
    Gen0_S=int(input("How many seniles in Generation 0? "))
    Srate_J=float(input("What is the survival rate for juveniles? "))
    Srate_A=float(input("What is the survival rate for adults? "))
    Srate_S=float(input("What is the survival rate for seniles? "))
    Birth_rate=int(input("What is the birth rate? "))
    return Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate

def display_values(Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate):
    print("\nThe amount of juveniles in Generation 0 is",Gen0_J)
    print("The amount of adults in Generation 0 is",Gen0_A)
    print("The amount of seniles in Generation 0 is",Gen0_S)
    print("The birth rate in Generation 0 is",Birth_rate)
    print("The survival rate for juveniles in Generation 0 is",Srate_J)
    print("The survival rate for adults in Generation 0 is",Srate_A)
    print("The survival rate for seniles in Generation 0 is",Srate_S)

Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate = generation_values()
display_values(Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate)

这是第一步。你知道吗

这样，“main”命名空间中的变量就与函数中的变量分开了。你知道吗

消除重复的下一步可能不是关心主命名空间中变量的分离，而是将它们视为元组：

data = generation_values()
display_values(*data)

消除重复和提高清晰度的进一步步骤包括：

• 在一个对象（名为tuple或其他对象）中组装数据
• 在对象的方法中请求并输出数据

Answer 2

正如其他人所说的，问题是对函数内部变量的赋值会创建新的变量，而不是将值赋给全局变量。这就是global关键字存在的原因。你知道吗

在本例中，我将考虑使用一个类，因为您有许多相关的状态值可以一起操作。你知道吗

class GenerationData(object):

    def __init__(self, gen_number):
        self.number = gen_number
        self.birth_rate = 0
        self.num_juveniles, self.num_adults, self.num_seniles = 0, 0, 0
        self.juvenile_rate, self.adult_rate, self.senile_rate = 0.0, 0.0, 0.0

    @classmethod
    def read(cls, gen_number):
        gen = cls(gen_number)
        gen.num_juveniles = read_integer(
            'How many juveniles in Generation {}?'.format(gen_number))
        gen.num_adults = read_integer(
            'How many adults in Generation {}?'.format(gen_number))
        gen.num_seniles = read_integer(
            'How many seniles in Generation {}?'.format(gen_number))
        gen.juvenile_rate = read_float(
            'What is the survival rate for juveniles? ')
        gen.adult_rate = read_float('What is the survival rate for adults? ')
        gen.senile_rate = read_float('What is the survival rate for seniles? ')
        gen.birth_rate = read_integer('What is the birth rate? ')

    def display(self):
        print('The amount of juveniles in Generation', self.number,
              'is', self.num_juveniles)
        print('The amount of adults in Generation', self.number,
              'is', self.num_adults)
        print('The amount of seniles in Generation', self.number,
              'is', self.num_seniles)
        print('The birth rate in Generation', self.number,
              'is', self.birth_rate)
        print('The survival rate for juveniles in Generation', self.number,
              'is', self.juvenile_rate)
        print('The survival rate for adults in Generation', self.number,
              'is', self.adult_rate)
        print('The survival rate for seniles in Generation', self.number,
              'is', self.senile_rate)


def read_integer(prompt):
    return int(raw_input(prompt))


def read_float(prompt):
    return float(raw_input(prompt))


first_generation = Generation.read(0)
first_generation.display()

这将使您在操作生成数据时变得更容易，因为生成数据都绑定到单个对象中。你知道吗

Answer 3

变量的范围不正确。[函数内、类内或模块内声明的变量在程序的更高级别上是不可访问的-这里是在注释中发布的a short description of python scoping rules]-在这种情况下，在generation_values()中分配给的变量是本地定义的。你知道吗

这样做肯定不是正确的方法，而是将变量声明为全局变量 generation_values()将解决您的问题：（定义什么是做这件事的“理想方法”取决于您在编程研究中的位置&这会让我们走得太远）

Gen0_J=0
Gen0_A=0
Gen0_S=0
Birth_rate=0
Srate_J=0
Srate_A=0
Srate_S=0
New_generations=5


def generation_values():

    global Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate

    Gen0_J=int(input("How many juveniles in Generation 0? "))
    Gen0_A=int(input("How many adults in Generation 0? "))
    Gen0_S=int(input("How many seniles in Generation 0? "))
    Srate_J=float(input("What is the survival rate for juveniles? "))
    Srate_A=float(input("What is the survival rate for adults? "))
    Srate_S=float(input("What is the survival rate for seniles? "))
    Birth_rate=int(input("What is the birth rate? "))
    return Gen0_J,Gen0_A,Gen0_S,Srate_J,Srate_A,Srate_S,Birth_rate


def display_values():
    print("\nThe amount of juveniles in Generation 0 is",Gen0_J)
    print("The amount of adults in Generation 0 is",Gen0_A)
    print("The amount of seniles in Generation 0 is",Gen0_S)
    print("The birth rate in Generation 0 is",Birth_rate)
    print("The survival rate for juveniles in Generation 0 is",Srate_J)
    print("The survival rate for adults in Generation 0 is",Srate_A)
    print("The survival rate for seniles in Generation 0 is",Srate_S)

generation_values()
display_values()

另一种处理方法是将变量作为参数传递给函数，并用赋值返回它们。。。但是它们有很多，传递它们可能会弄乱你的代码。你知道吗

您还可以将它们聚集在一个元组中，或者将它们包装在一个类中。你知道吗