18 19 20 pyif文比較演算子アサートasserts

              （if、else elif）
# coding:utf-8

python                 
#      （if、else elif）
'''
if logic_expression:
    statement1
    statement2
    statement3
    ... ...
    statementn
elif logic_expression:
    statement1
    statement2
    ... ...
    statementn
else:
    statement1
    statement2
    ... ...
    statementn
otherstatement
'''
n = 3
if n == 3:            # python         4     1 tab 
    print("n == 3")
    print("hello world")
#                  
print("------------------")

w = 2
if w == 1:
    print("w ==1")
else:               #   else      
    print("w !=1")
print("------------------")  

n = 5
if n == 3:
    print("n == 3")
    print("xyz")
elif n == 4:
    print("n == 4")
    print("ddd")
elif n == 5:
    print("n == 5")
    print("xxx")
else:
    print("n != 3")
    print("abc")

name = input("       ：")
if name.startswith("B"):     #          ，     B          
    print("   B  ")
elif name.startswith("F"):
    print("   F  ")
elif name.startswith("T"):
    print("   T  ")
else:
    print("         ") 

        shell  
[hadoop@dev-hadoop-test03 majihui_test]$ cat a.sh 
#!/bin/bash

read -t 6 -p "pls input you name:" name

if [ $name == "majihui" ];then
        echo "    :$name"
elif [ $name == "mjh" ];then
        echo "    :$name"
else 
        echo "       "
fi
[hadoop@dev-hadoop-test03 majihui_test]$ sh a.sh 
pls input you name:majihui
    :majihui
[hadoop@dev-hadoop-test03 majihui_test]$ sh a.sh
pls input you name:mjh
    :mjh
[hadoop@dev-hadoop-test03 majihui_test]$ sh a.sh
pls input you name:sdd
       

[root@localhost if]# cat ifjiaoben5.sh 【    bug                   】              ！
#!/bin/bash
if [ $1 -lt $2 ];then
        echo "$1$2"
fi
[root@localhost if]# sh ifjiaoben5.sh 1 2
1<2
[root@localhost if]# sh ifjiaoben5.sh 2 1
2>1
[root@localhost if]# sh ifjiaoben5.sh 1 1
1=1

---------------------------------------------------------------------
    if          
        

# coding:utf-8
name = input("      ？")
if name.startswith("Bill"):
    if name.endswith("Gates"):
        print("  Bill Gates  ")
    elif name.endswith("Clinton"):
        print("       ")
    else:
        print("    ")
    print("hello world")
elif name.startswith(" "):
    if name.endswith(" "):
        print("      ")
    else:
        print("    ")
else:
    print("    ")
---------------------------
           
# coding:utf-8
name = input("    A B C     ")
if name.startswith("A"):   #   A     
    if name.endswith("a"): #   a     
        print("     Aa")
    elif name.endswith("b"):
        print("     Ab")
    else:
        print("          ")
    print("hello world") #                 hello world
elif name.startswith(" "):
    if name.endswith(" "):
        print("      ")
    else:
        print("    ")
else:
    print("        ")

——————————————————————————————————————————————————————————————————————————————
         
# coding:utf-8
#      

'''
x == y  x  y
x < y   x    y
x > y   x    y
x <= y  x      y
x >= y  x      y
x != y  x     y

x is y      x y      
x is not y  x y            x y        2      

x in y   x   y     ，y   [1,2,3,4]，1 in y,10 in y
x not in y  x   y     

                 boolean   ******

shell  
         
 []                 (()) [[]]              
-eq                             ==          equal      
-ne             !=                         not equal      
-gt             >                           
-ge             >=                              
-lt             <                             
-le             <=                              

'''
print("Hello" == "Hello")  #  True
print("hello" == "Hello")  #  flase   python           
# print("hello" = "Hello")  #       =         

print(10 == 20)  #  false

print("hello" > "Hello")        #  true        h         H
print("hello" > "hello world")  #  flase         hello                               

list = [1,2,3,4,5]  #     
print(1 in list)    #  true
print(10 in list)   #  false
print(10 not in list)  #  true 

print("--------------------------------")
#                  
x = 40
y = 30
s1 = "Hello"
s2 = "World"
if x < y:
    print("x < y")
else:
    print("x >= y")
# or            shell   ||
# and            shell   && 

shell   ：
     
 []                [[]]                        
-a  【and 】      &&          “ ”     ，   
-o  【or 】       ||          “ ”          
！               ！           “ ”     

'''
   and   True and True == True  
   or    False or False == False
'''
if x < y and s1 < s2:
    print("    ")
elif not s1 > s2:
    print("      ")
else:
    print("     ") 

      （Assertions
//                     ，     
           +     

#   （assertions)
'''
    if not condition
        crash program
                           //    TDD      
    TDD（Test-driven development） #                                 
                                 #TDD                                            x y z
              x > 20 y < 10 z == 50               ，              
    x y z

    x > 20
    if x <= 20:
           
    y < 10
    z == 50
'''

value = 20
assert value > 10     #                           

value = 4
assert value > 10     #       ，                。 
     ：
/Users/majihui/pycharm_work/venv/bin/python /Users/majihui/pycharm_work/test05.py
Traceback (most recent call last):
  File "/Users/majihui/pycharm_work/test05.py", line 2, in 
    assert value > 10 
AssertionError

Process finished with exit code 1