带有示例的Python逻辑运算符

运算符用于对值和变量执行操作。这些是执行算术和逻辑计算的特殊符号。运算符操作的值称为Operand 。

Table of Content

• Logical operators
  • Logical AND operator
  • Logical OR operator
  • Logical NOT operator
• Order of evaluation of logical operators

逻辑运算符

在Python中，逻辑运算符用于条件语句（真或假）。它们执行逻辑与、逻辑或和逻辑非操作。

OPERATOR	DESCRIPTION	SYNTAX
and	Logical AND: True if both the operands are true	x and y
or	Logical OR: True if either of the operands is true	x or y
not	Logical NOT: True if operand is false	not x

逻辑与运算符

如果两个操作数都为 True ，则逻辑运算符返回True ，否则返回False 。

示例 #1：

# Python program to demonstrate
# logical and operator
  
a = 10
b = 10
c = -10
  
if a > 0 and b > 0:
    print("The numbers are greater than 0")
  
if a > 0 and b > 0 and c > 0:
    print("The numbers are greater than 0")
else:
    print("Atleast one number is not greater than 0")

输出：

The numbers are greater than 0
Atleast one number is not greater than 0

示例 #2：

# Python program to demonstrate
# logical and operator
  
a = 10
b = 12
c = 0
  
if a and b and c:
    print("All the numbers have boolean value as True")
else:
    print("Atleast one number has boolean value as False")

输出：

Atleast one number has boolean value as False

注意：如果在使用 and运算符时第一个表达式的计算结果为 false，则不会计算其他表达式。

逻辑或运算符

如果任一操作数为 True，则逻辑或运算符返回 True。

示例 #1：

# Python program to demonstrate
# logical or operator
  
a = 10
b = -10
c = 0
  
if a > 0 or b > 0:
    print("Either of the number is greater than 0")
else:
    print("No number is greater than 0")
  
if b > 0 or c > 0:
    print("Either of the number is greater than 0")
else:
    print("No number is greater than 0")

输出：

Either of the number is greater than 0
No number is greater than 0

示例 #2：

# Python program to demonstrate
# logical and operator
  
a = 10
b = 12
c = 0
  
if a or b or c:
    print("Atleast one number has boolean value as True")
else:
    print("All the numbers have boolean value as False")

输出：

Atleast one number has boolean value as True

注意：如果在使用 or运算符时第一个表达式的计算结果为 True，则不会计算进一步的表达式。

逻辑非运算符

逻辑非运算符使用单个布尔值。如果布尔值为True ，则返回False ，反之亦然。

例子：

# Python program to demonstrate
# logical not operator
  
a = 10
  
if not a:
    print("Boolean value of a is True")
  
if not (a%3 == 0 or a%5 == 0):
    print("10 is not divisible by either 3 or 5")
else:
    print("10 is divisible by either 3 or 5")

输出：

10 is divisible by either 3 or 5

逻辑运算符的求值顺序

在多个运算符的情况下， Python总是从左到右计算表达式。这可以通过下面的例子来验证。

例子：

# Python program to demonstrate
# order of evaluation of logical 
# operators
  
def order(x):
    print("Method called for value:", x)
    return True if x > 0 else False
      
a = order
b = order
c = order
  
if a(-1) or b(5) or c(10):
    print("Atleast one of the number is positive")

输出：

Method called for value: -1
Method called for value: 5
Atleast one of the number is positive