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Defining a signal in the __init__ function of a class versus defining it outside the __init__ function has a significant difference in terms of scope and visibility.

1. Defining in __init__:
   • When you define a signal in the __init__ function of a class, it becomes an instance attribute of that class. This means that each instance of the class will have its own signal attribute.
   • Signals defined in __init__ are accessible only within the instance of the class where they are defined. Other instances of the same class will have their own separate signal attributes.

Example:

from PySide6.QtCore import QObject, Signal

class MyClass(QObject):
    def __init__(self):
        super().__init__()
        self.my_signal = Signal()

# Usage
obj1 = MyClass()
obj2 = MyClass()

# obj1 and obj2 have their own separate instances of my_signal

2. Defining outside __init__:
   • When you define a signal outside the __init__ function (as a class attribute), it becomes a class-level attribute.
   • Signals defined outside __init__ are shared among all instances of the class. They behave like static members of the class.

Example:

from PySide6.QtCore import QObject, Signal

class MyClass(QObject):
    my_signal = Signal()

# Usage
obj1 = MyClass()
obj2 = MyClass()

# obj1 and obj2 share the same instance of my_signal

In Summary:

• If you define a signal in the __init__ function, each instance of the class will have its own signal attribute. This can be useful if you need different instances to emit signals independently.
• If you define a signal outside the __init__ function, it becomes a class-level attribute shared among all instances. This can be useful if you want all instances to share the same signal, such as for notifying about global events or state changes.