*Memo:
- My post explains global and nonlocal with 3 classes and 3 functions (2).
- My post explains global and nonlocal with 3 classes and 3 functions (3).
- My post explains global and nonlocal with 3 functions (1).
- My post explains global and nonlocal with 3 functions (2).
- My post explains global and nonlocal with 3 functions (3).
- My post explains global and nonlocal with 2 classes and 3 functions (1).
- My post explains global and nonlocal with 2 classes and 3 functions (2).
- My post explains global and nonlocal with 2 classes and 3 functions (3).
- My post explains global and nonlocal with 2 functions or generators.
With 3 classes and 3 functions, there are 4 kinds of variables from the viewpoint of third() as shown below:
- A global variable is the variable out of any functions and classes.
- A non-local variable is the variable within outer functions.
- A local variable is the variable which is within its function.
- A class variable is the variable within its class.
- A global and non-local variable can be accessed from a function as long as the function is called and run after them even if the function is defined before them as show in unintuitive version.
<Intuitive version>:
""" It's from the viewpoint of `third()` """ num = 2 # <- Global variable print(num) # 2 class Cls1: num = 3 # <- Class variable print(num) # 3 def first(self): num = 4 # <- Non-local variable print(num) # 4 class Cls2: num = 5 # <- Class variable print(num) # 5 def second(self): num = 6 # <- Non-local variable print(num) # 6 class Cls3: num = 7 # <- Class variable print(num) # 7 def third(self): num = 8 # <- Local variable print(num) # 8 Cls3().third() Cls2().second() Cls1().first() <Unintuitive version>:
""" It's from the viewpoint of `third()` """ class Cls1: def first(self): class Cls2: def second(self): class Cls3: def third(self): num = 8 # <- Local variable print(num) # 8 num = 7 # <- Class variable print(num) # 7 num = 6 # <- Non-local variable print(num) # 6 Cls3().third() num = 5 # <- Class variable print(num) # 5 num = 4 # <- Non-local variable print(num) # 4 Cls2().second() num = 3 # <- Class variable print(num) # 3 num = 2 # <- Global variable print(num) # 2 Cls1().first() A global statement can refer to a global variable as shown below:
*Memo:
- The doc explains the rules for local and global variables in Python.
<Read(Intuitive version)>:
""" It's from the viewpoint of `third()` """ num = 2 # <- 〇 class Cls1: num = 3 # <- ✖ def first(self): num = 4 # <- ✖ class Cls2: num = 5 # <- ✖ def second(self): num = 6 # <- ✖ class Cls3: num = 7 # <- ✖ def third(self): global num # Here print(num) # 2 Cls3().third() Cls2().second() Cls1().first() """ It's from the viewpoint of `third()` """ # num = 2 # <- Commented class Cls1: num = 3 # <- ✖ def first(self): num = 4 # <- ✖ class Cls2: num = 5 # <- ✖ def second(self): num = 6 # <- ✖ class Cls3: num = 7 # <- ✖ def third(self): global num # NameError: name 'num' is not defined. print(num) # Did you mean: 'self.num'? Cls3().third() Cls2().second() Cls1().first() <Read(Unintuitive version)>:
""" It's from the viewpoint of `third()` """ class Cls1: def first(self): class Cls2: def second(self): class Cls3: def third(self): global num # Here print(num) # 2 num = 7 # <- ✖ num = 6 # <- ✖ Cls3().third() num = 5 # <- ✖ num = 4 # <- ✖ Cls2().second() num = 3 # <- ✖ num = 2 # <- 〇 Cls1().first() """ It's from the viewpoint of `third()` """ class Cls1: def first(self): class Cls2: def second(self): class Cls3: def third(self): global num # NameError: name 'num' is not defined. print(num) # Did you mean: 'self.num'? num = 7 # <- ✖ num = 6 # <- ✖ Cls3().third() num = 5 # <- ✖ num = 4 # <- ✖ Cls2().second() num = 3 # <- ✖ # num = 2 # <- Commented Cls1().first() <Change(Intuitive version)>:
""" It's from the viewpoint of `third()` """ num = 2 # <- 〇 class Cls1: num = 3 # <- ✖ def first(self): num = 4 # <- ✖ class Cls2: num = 5 # <- ✖ def second(self): num = 6 # <- ✖ class Cls3: num = 7 # <- ✖ def third(self): global num # Here num += 10 # Here print(num) # 12 Cls3().third() print(num) # 6 Cls2().second() print(num) # 4 Cls1().first() print(num) # 12 """ It's from the viewpoint of `third()` """ # num = 2 # <- Commented class Cls1: num = 3 # <- ✖ def first(self): num = 4 # <- ✖ class Cls2: num = 5 # <- ✖ def second(self): num = 6 # <- ✖ class Cls3: num = 7 # <- ✖ def third(self): global num # NameError: name 'num' is not defined. num += 10 # Did you mean: 'self.num'? print(num) Cls3().third() print(num) Cls2().second() print(num) Cls1().first() print(num) <Change(Unintuitive version)>:
""" It's from the viewpoint of `third()` """ class Cls1: def first(self): class Cls2: def second(self): class Cls3: def third(self): global num # Here num += 10 # Here print(num) # 12 num = 7 # <- ✖ num = 6 # <- ✖ Cls3().third() print(num) # 6 num = 5 # <- ✖ num = 4 # <- ✖ Cls2().second() print(num) # 4 num = 3 # <- ✖ num = 2 # <- 〇 Cls1().first() print(num) # 12 """ It's from the viewpoint of `third()` """ class Cls1: def first(self): class Cls2: def second(self): class Cls3: def third(self): global num # NameError: name 'num' is not defined. num += 10 # Did you mean: 'self.num'? print(num) num = 7 # <- ✖ num = 6 # <- ✖ Cls3().third() print(num) num = 5 # <- ✖ num = 4 # <- ✖ Cls2().second() print(num) num = 3 # <- ✖ # num = 2 # <- Commented Cls1().first() print(num) 
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