Can elif be used alone in python?

In Python, you can use if-elif-else statements to implement multiple conditional judgments.

else and elif statements can also be called clauses, because they cannot be used independently. Both appear inside if, for, and while statements. The else clause can add a choice; the elif clause is used when more conditions need to be checked, and is used together with if and else. elif is the abbreviation of else if.

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How to use if and else statements

Let's use an example to illustrate how if and else statements are used together. First, set an integer variable. Let's see whether this variable is larger or smaller than 0.

>>>num = 0
>>>if num > 0 :
>>>    print '这个数比0大'
>>>else :
>>>    print '这个数比0小'

First, the program determines whether the condition of the if statement is true. If it is true, the contents of the if statement block will be executed. If this num > 0, then print 'This number is greater than 0' will be executed. But num = 0, obviously the condition of the if statement is false, and the corresponding statement block will not be executed; if the first statement block is not executed, then the second statement block will be executed.
The calculation result of the program is ‘this number is smaller than 0’. Some people may have doubts. The result that this number is equal to 0 should be more accurate. So why does this result occur? Taking the data in the case as an example, the judgment check method of if and else statements is that if num > 0, it will output 'this number is larger than 0', otherwise it will output 'this number is smaller than 0'. Because there is no condition to set for else, when the if condition cannot be satisfied and is false, the else clause block will be output unconditionally.
For this question, we need to add another condition to it, so that the result will be more correct. At this time, the elif clause will be used.

How to use if, else, and elif statements

>>>num = 0
>>>if num > 0 :
>>>    print '这个数比0大'
>>>elif num < 0 :
>>>    print &#39;这个数比0小&#39;
>>>else :
>>>    print &#39;这个数是0&#39;

The program judges if and elif respectively. If the condition is not true, then Output the contents of the else statement block. The result of running the program is: This number is 0

When using if and else, elif statements, please pay attention to the following two points:

1, else , elif is a sub-block and cannot be used independently
2. An if statement can contain multiple elif statements, but there can only be one else statement at the end

else is in while, for The role of loop statements

In python, you can use the else clause in while and for loops. It will only be executed after the loop ends. If the break statement is used at the same time, then The else clause block will be skipped. So note that the else clause and the break statement cannot be used at the same time!

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