9. Conditional statement

9.1 basic grammar

1. Basic format

if condition:
   doSomething
elif condition:
   doSomething
   
   ...
   
else:
   doSomething

2. Nesting format

if condition:
   if condition:
      doSomething
   else: 
      doSomething
elif condition:
   if condition:
      doSomething
   elif condition:
      doSomething
   else: 
      doSomething
      
      ...
      
else
   if condition:
      doSomething
   else: 
      doSomething

Schematic diagram of basic variation form of   is as follows:

9.2 ternary operators

[result = ] TrueResult if condition else FalseResult

For the children's shoes of                      .

9.3 dictionary implementation switch condition judgment

def add(x:int,y:int)->int:
    print( x+y)

def sub(x:int,y:int)->int:
    print( x-y)

def mul(x:int,y:int)->int:
    print( x*y)

def div(x:int,y:int)->int:
    if y:
       print( x/y)

def simpleCaculator(operator:str,x:int,y:int)->None:
    dic={
        "+":add,
        "-":sub,
        "*":mul,
        "/":div,
    }
    return dic.get(operator)(x,y)

if __name__ == '__main__':
    simpleCaculator("+", 1, 2)
    simpleCaculator("-", 1, 2)
    simpleCaculator("*", 1, 2)
    simpleCaculator("/", 1, 2)

3
-1
2
0.5

9.4 example code

The    example code is as follows:

tmpStr=int(input("Please enter a number:"))

if tmpStr<0:
    print("The number you entered is less than 0")
elif tmpStr<100:
    if 0<=tmpStr<=50:
         print("The number you entered is between[0,50]")
    elif 50<tmpStr<=100:
        print("The number you entered is between(50,100]")
else:
    if 100<tmpStr<=999:
        print("The number you entered is between(100,999]")
    else:
        print("The number you entered is too large, so the information will not be output for the time being")

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