*Memo:
- 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 (3).
A nonlocal statement can refer to a non-local variable as shown below:
<Read(Intuitive version)>:
""" It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): num = 5 # <- ✖ def second(): num = 6 # <- 〇 def third(): nonlocal num # Here print(num) # 6 third() second() Cls1().Cls2().first() """ It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): num = 5 # <- 〇 def second(): # num = 6 # <- Commented def third(): nonlocal num # Here print(num) # 5 third() second() Cls1().Cls2().first() """ It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): # num = 5 # <- Commented def second(): # num = 6 # <- Commented def third(): nonlocal num # SyntaxError: no binding print(num) # for nonlocal 'num' found third() second() Cls1().Cls2().first() <Read(Unintuitive version)>:
""" It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # Here print(num) # 6 num = 6 # <- 〇 third() num = 5 # <- ✖ second() num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() """ It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # Here print(num) # 5 # num = 6 # <- Commented third() num = 5 # <- 〇 second() num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() """ It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # SyntaxError: no binding print(num) # for nonlocal 'num' found # num = 6 # <- Commented third() # num = 5 # <- Commented second() num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() <Change(Intuitive version)>:
""" It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): num = 5 # <- ✖ def second(): num = 6 # <- 〇 def third(): nonlocal num # Here num += 10 # Here print(num) # 16 third() print(num) # 16 second() print(num) # 5 Cls1().Cls2().first() print(num) # 2 """ It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): num = 5 # <- 〇 def second(): # num = 6 # <- Commemnted def third(): nonlocal num # Here num += 10 # Here print(num) # 15 third() print(num) # 15 second() print(num) # 15 Cls1().Cls2().first() print(num) # 2 """ It's from the viewpoint of `third()` """ num = 2 # <- ✖ class Cls1: num = 3 # <- ✖ class Cls2: num = 4 # <- ✖ def first(self): # num = 5 # <- Commemnted def second(): # num = 6 # <- Commemnted def third(): nonlocal num # SyntaxError: no binding num += 10 # for nonlocal 'num' found print(num) third() print(num) second() print(num) Cls1().Cls2().first() print(num) <Change(Unintuitive version)>:
""" It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # Here num += 10 # Here print(num) # 16 num = 6 # <- 〇 third() print(num) # 16 num = 5 # <- ✖ second() print(num) # 5 num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() print(num) # 2 """ It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # Here num += 10 # Here print(num) # 15 # num = 6 # <- Commemnted third() print(num) # 15 num = 5 # <- 〇 second() print(num) # 15 num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() print(num) # 2 """ It's from the viewpoint of `third()` """ class Cls1: class Cls2: def first(self): def second(): def third(): nonlocal num # SyntaxError: no binding num += 10 # for nonlocal 'num' found print(num) # num = 6 # <- Commemnted third() print(num) # num = 5 # <- Commemnted second() print(num) num = 4 # <- ✖ num = 3 # <- ✖ num = 2 # <- ✖ Cls1().Cls2().first() print(num) 
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