Python study Note 3: logical operators

 

Python has three logical operations: and, or, and not. Corresponds to and, Or, rather. Example:

Python has three logical operations: and, or, and not. Corresponds to and, Or, rather.
Example:

 

 1 #coding:utf-8
2  test1 = 12
3 test2 = 0
4  print (test1 > test2) and (test1 > 14)  #result = False
5  print (test1 < test2) or (test1 > -1)   #result = True
6  print (not test1)                       #result = False
7  print (not test2)                       #result = True

 

 

 

 

Strictly speaking, the operands of logical operators should be boolean expressions. But Python is flexible in processing this. Even if the operands are numbers, the interpreter regards them as "expressions ". The Boolean value of A number other than 0 is 1 and 0 is 0. For example:

 1 #coding:utf-8
2  test1 = 12
3 test2 = 0
4  print (test1 and test2)  #result = 0
5  print (test1 or test2)   #result = 12
6  print (not test1)        #result = Flase
7  print (not test2)        #reslut = True

 

In Python, the Null String is false, and the non-null string is true. The non-zero number is true. The logic operation rule between numbers and strings and between strings is: For the and operator: If the expression on the left is true, the value returned by the entire expression is the value of the expression on the right. Otherwise, returns the value of the Left expression for the or operator. If the expressions on both sides are true, the result of the entire expression is the value of the Left expression. If the expression is true or false, the return value of the true value expression is false. If both values are false, such as null and 0, the return value is the value on the right. (Null or 0) Example:

  1 #coding:utf-8
 2  test1 = 12
 3 test2 = 0
 4 test3 = ''
 5 test4 = "First"
 6  print test1 and test3   #result = ''
 7  print test3 and test1   #result = ''
 8  print test1 and test4   #result = "First"
 9  print test4 and test1   #result = 12
10  print test1 or test2    #result = 12
11  print test1 or test3    #result = 12
12  print test3 or test4    #result = "First"
13  print test2 or test4    #result = "First"
14  print test1 or test4    #result = 12
15  print test4 or test1    #result = "First"
16  print test2 or test3    #result = ''
17  print test3 or test2    #result = 0

 

 

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