如何在 python 中的 class 中定义全局变量

Question

I want to take a variable outside the class but not outside of the file. I have a condition outside the class but I have to use it in the class too. Have can i do that?

This is the sample to try if it is working. I want to erase the input part and do with global variable.

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":

I tried this one but not working. It gives name "ask" not defined.

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

This is the outside of class.

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

If you just want to define your variable outside of the class you don't need to use the global keyword unless you plan on modifying it. If you just want to read the variable and not modify it you could just do something like.

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

I'm not exactly sure what you are trying to do but perhaps you just need to have global ask above your ask=input("") outside the class.

Answer 3

I found the solution. Thank you from Barmar. It worked.

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

if you're referring to a static, something available from Class.val and instance.val referencing the same thing; you can declare one in the class body

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)