如何在 python 中的 class 中定义全局变量

Question

我想在 class 之外取一个变量，但不在文件之外。 我在 class 之外有一个条件，但我也必须在 class 中使用它。 我可以这样做吗？

如果它有效，这是尝试的示例。 我想擦除输入部分并使用全局变量。

class ComplexMethods:
    ask = input("What type you are writing? (absolute value and phase angle or real and imaginary parts)")
    if ask == "real and imaginary parts":

我试过这个但不工作。 它给出了未定义的名称“询问”。

class ComplexMethods:
     global ask
     if ask == "real and imaginary parts":

这是 class 的外部。

ask = input("What type you are writing? (absolute value and phase angle or real and imaginary parts)")
if ask == "real and imaginary parts":
    firstcomplexreal = float(input("Enter real part of first complex number: "))
    firstcompleximaginary = float(input("Enter imaginary part of first complex number: "))
    secondcomplexreal = float(input("Enter real part of second complex number: "))
    secondcompleximaginary = float(input("Enter imaginary part of second complex number: "))
    complexnumbers = ComplexMethods(firstcomplexreal, firstcompleximaginary, secondcomplexreal,
                                    secondcompleximaginary)

Answer 1

如果您只想在 class 之外定义变量，则不需要使用global关键字，除非您打算修改它。 如果您只想读取变量而不修改它，您可以执行类似的操作。

ask = input("What type you are writing? (absolute value and phase angle or real and imaginary parts)")

class ComplexMethods:
    if ask == "real and imaginary parts":
        pass

if ask == "real and imaginary parts":
    firstcomplexreal = float(input("Enter real part of first complex number: "))
    firstcompleximaginary = float(input("Enter imaginary part of first complex number: "))
    secondcomplexreal = float(input("Enter real part of second complex number: "))
    secondcompleximaginary = float(input("Enter imaginary part of second complex number: "))
    complexnumbers = ComplexMethods(firstcomplexreal, firstcompleximaginary, secondcomplexreal,
                                    secondcompleximaginary)

Answer 2

我不确定您要做什么，但也许您只需要在 class 之外的ask=input("")上方进行global ask 。

Answer 3

我找到了解决方案。 来自巴尔玛的感谢。 有效。

ask = input("What type you are writing? (absolute value and phase angle or real and imaginary parts)")


class ComplexMethods:
    global ask
    if ask == "real and imaginary parts":

Answer 4

如果您指的是 static，则可以从Class.val和instance.val获得相同的东西； 您可以在 class 正文中声明一个

class A:
  val = None # Static variable
  def __init__(self, x, y):
    # Instance variables
    self.x = x
    self.y = y

inst_1 = A(2, 3)
inst_2 = A("a", "b")

print(A.val)
# static can't be modified via instance, only A
A.val = "abcd"
print(inst_2.val) # static modified across As

# Unique to each instance
print(inst_1.x)
print(inst_2.x)