How to Manually Deduce the Results of Python\'s Unpacking, Extended Unpacking, and Nested Extended Unpacking Expressions?

Understanding unpacking, extended unpacking and nested extended unpacking

Questions

Consider the following expressions, noting that some are repeated to express "context."

a, b = 1, 2                          # 简单序列赋值
a, b = ['green', 'blue']             # 列表赋值
a, b = 'XY'                          # 字符串赋值
a, b = range(1,5,2)                  # 任何可迭代的对象都可以

                                     # 嵌套的序列赋值

(a,b), c = "XY", "Z"                 # a = 'X', b = 'Y', c = 'Z' 

(a,b), c = "XYZ"                     # ERROR -- 太多要解包的值
(a,b), c = "XY"                      # ERROR -- 需要超过 1 个要解包的值

(a,b), c, = [1,2],'this'             # a = '1', b = '2', c = 'this'
(a,b), (c,) = [1,2],'this'           # ERROR -- 太多要解包的值


                                     # 扩展的序列解包

a, *b = 1,2,3,4,5                    # a = 1, b = [2,3,4,5]
*a, b = 1,2,3,4,5                    # a = [1,2,3,4], b = 5
a, *b, c = 1,2,3,4,5                 # a = 1, b = [2,3,4], c = 5

a, *b = 'X'                          # a = 'X', b = []
*a, b = 'X'                          # a = [], b = 'X'
a, *b, c = "XY"                      # a = 'X', b = [], c = 'Y'
a, *b, c = "X...Y"                   # a = 'X', b = ['.','.','.'], c = 'Y'

a, b, *c = 1,2,3                     # a = 1, b = 2, c = [3]
a, b, c, *d = 1,2,3                  # a = 1, b = 2, c = 3, d = []

a, *b, c, *d = 1,2,3,4,5             # ERROR -- 赋值中存在两个星号表达式

(a,b), c = [1,2],'this'              # a = '1', b = '2', c = 'this'
(a,b), *c = [1,2],'this'             # a = '1', b = '2', c = ['this']

(a,b), c, *d = [1,2],'this'          # a = '1', b = '2', c = 'this', d = []
(a,b), *c, d = [1,2],'this'          # a = '1', b = '2', c = [], d = 'this'

(a,b), (c, *d) = [1,2],'this'        # a = '1', b = '2', c = 't', d = ['h', 'i', 's']

*a = 1                               # ERROR -- 目标必须在列表或元组中
*a = (1,2)                           # ERROR -- 目标必须在列表或元组中
*a, = (1,2)                          # a = [1,2]
*a, = 1                              # ERROR -- 'int' 对象不可迭代
*a, = [1]                            # a = [1]
*a = [1]                             # ERROR -- 目标必须在列表或元组中
*a, = (1,)                           # a = [1]
*a, = (1)                            # ERROR -- 'int' 对象不可迭代

*a, b = [1]                          # a = [], b = 1
*a, b = (1,)                         # a = [], b = 1

(a,b),c = 1,2,3                      # ERROR -- 太多要解包的值
(a,b), *c = 1,2,3                    # ERROR - 'int' 对象不可迭代
(a,b), *c = 'XY', 2, 3               # a = 'X', b = 'Y', c = [2,3]


                                     # 扩展的序列解包 -- 嵌套

(a,b),c = 1,2,3                      # ERROR -- 太多要解包的值
*(a,b), c = 1,2,3                    # a = 1, b = 2, c = 3

*(a,b) = 1,2                         # ERROR -- 目标必须在列表或元组中
*(a,b), = 1,2                        # a = 1, b = 2

*(a,b) = 'XY'                        # ERROR -- 目标必须在列表或元组中
*(a,b), = 'XY'                       # a = 'X', b = 'Y'

*(a, b) = 'this'                     # ERROR -- 目标必须在列表或元组中
*(a, b), = 'this'                    # ERROR -- 要解包的值过多
*(a, *b), = 'this'                   # a = 't', b = ['h', 'i', 's']

*(a, *b), c = 'this'                 # a = 't', b = ['h', 'i'], c = 's'

*(a,*b), = 1,2,3,3,4,5,6,7           # a = 1, b = [2, 3, 3, 4, 5, 6, 7]

*(a,*b), *c = 1,2,3,3,4,5,6,7        # ERROR -- 赋值中存在两个星号表达式
*(a,*b), (*c,) = 1,2,3,3,4,5,6,7     # ERROR -- 'int' 对象不可迭代
*(a,*b), c = 1,2,3,3,4,5,6,7         # a = 1, b = [2, 3, 3, 4, 5, 6], c = 7
*(a,*b), (*c,) = 1,2,3,4,5,'XY'      # a = 1, b = [2, 3, 4, 5], c = ['X', 'Y']

*(a,*b), c, d = 1,2,3,3,4,5,6,7      # a = 1, b = [2, 3, 3, 4, 5], c = 6, d = 7
*(a,*b), (c, d) = 1,2,3,3,4,5,6,7    # ERROR -- 'int' 对象不可迭代
*(a,*b), (*c, d) = 1,2,3,3,4,5,6,7   # ERROR -- 'int' 对象不可迭代
*(a,*b), *(c, d) = 1,2,3,3,4,5,6,7   # ERROR -- 赋值中存在两个星号表达式


*(a,b), c = 'XY', 3                  # ERROR -- 需要超过 1 个要解包的值
*(*a,b), c = 'XY', 3                 # a = [], b = 'XY', c = 3
(a,b), c = 'XY', 3                   # a = 'X', b = 'Y', c = 3

*(a,b), c = 'XY', 3, 4               # a = 'XY', b = 3, c = 4
*(*a,b), c = 'XY', 3, 4              # a = ['XY'], b = 3, c = 4
(a,b), c = 'XY', 3, 4                # ERROR -- 要解包的值过多

How to correctly derive the result of such an expression manually?

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