运算(算术,逻辑,赋值)

算术运算:

　　+ (加法运算,对字符串起拼接作用)

　　- (减法运算)

　　* (乘法运算,对字符串起重复作用)

　　/ (除法运算)

　　// (整除运算)

　　** (幂运算)

赋值运算:

 # "=" : c = a + b,将a+b的值赋给c
 # "+=": a+ = b 等效于 a = a + b
 # "-=": a- = b 等效于 a = a - b
 # "-=": a - = b 等效于a = a - b 
 # "*=": a* = b 等效于 a = a * b
 # "/=": a/ = b 等效于 a = a / b
 # "%=": a% = b 等效于 a = a % b
 # "**=": a** = b 等效于 a = a ** b
 # "//=": a// = b 等效于 a = a // b

逻辑运算:

　　and: 两边必须全为真结果才为真,存在假结果就是假.

　　or:  两边有一个为真结果就为真,两边全是假结果才为假.

　　not: 非真即假,非假即真

逻辑运算时,先判断比较的结果是真还是假,and, or,not同时存在时,先计算括号里的,然后计算not,再计算and,最后计算or.

num or 0 ==>num; 　0 or num ==>num;     num1 or num2 ==>num1;

num and 0 ==>0;　　0 and num ==>0;        num1 and num2 ==>num2;

#T为True, F为False
print(not 2 > 1 and 3 < 4 or 4 > 5 and 2 > 1 and 9 > 8 or 7 < 6 ) #False
#F and T or F and T and T or F
#F or F and T or F
#F or F or F
#F

print(8 or 3 and 4 or 2 and 0 or 9 and 7) #8
#print(8 or 3 and 4 or 2 and 0 or 9 and 7)
#8 or 4 or 0 or 7
#8

print(3 > 1 and 2 or 2 < 3 and 3 and 4 or 3 > 2) #2
#T and 2 or F and 3 and 4 or T
#2 or F and 4 or T
#2 OR F or T
#2

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