Ⅰ. Operator(运算符)
1. Assignment operator (赋值运算符)
Simple assignment operators:

=

Compound assignment operators:

+=, -=, *=, /=

%=, **=, //=

2. Identifier (标识符)
a) An identifier is a name given to a variable, function, class or module.
b) be a combination of:
letters in lowercase (a to z) or uppercase (A to Z), 
numbers (0 to 9) ,
underscores( _ ).
c) must start with a letter or an underscore, and cannot start with a number !
d) cannot be “language reserved words” (keywords).

3. Arithmetic operators (算术运算符)

+,-,*,/

%  # remainder 取模(取余)
** # exponentiation 幂
// # floor division 取整

4.Comparison operators (比较运算符)

==,!=,>,<,>=,<=

5.Logical operators (逻辑运算符)

and &
or |
not

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