Python Basic Learning switch statement

switch Syntax structure :

The switch statement is used to write a multi-branch structure program, similar to the If...elif...eles statement.

The branching result of the expression of the Swtch statement is clearer than the If...elif...lese statement, and the code is more readable.

# # # #python并没有提供switch语句 ######

However: Python can implement the switch statement functionality through a dictionary.

Implementation method:

Define a dictionary

Call the dictionary get () to get the appropriate expression

Example:

>>> 6/41>>> 6.0/41.5>>> from __future__ import division>>> 5/22.5

# __future__ Module Division precise Division

Here is a calculator:

#!/usr/bin/python#coding:utf-8from __future__ import divisiondef jia (x, y):     return x+ydef jian (x, y):     return x-ydef chu (x, y):     return x/ydef cheng (x, y):         return  x*ydef operator (x,o,y):     x =int (Raw_input ("plese somthing  Number: "))     y =int (Raw_input (" Plese somthing number: "))      o = raw_input ("plese somthing +/*-:")     if o ==  ' + ':         print jia (x, y)     elif o  ==  ' * ':         print cheng (x, y)      elif o ==  '/':         print chu (x, y)      elif o ==  '-':         print jian (x, y)     else :         passprint operator (' x ', ' o ', ' y ')

#注意三次判断是多余的, and if the symbol is wrong, execution is empty, the efficiency is not very good

If you write a calculator via switch

[[email protected] tools]# cat switch.py #!/usr/bin/python#coding:utf-8from __ Future__ import divisiondef jia (x, y):     return x+ydef jian (x, y):     return x-ydef chu (x, y):     return x/ydef cheng (x, y):     return x*yoperator = {"+": Jia, "-": Jian, "*": Cheng, "/": Chu}print  jia (2,4) print jiaprint operator["+"] (3,4)                                   #通过字典取值, eliminating the link of judgment; [[email protected] tools]# python switch.py  6<function jia at 0x7fc3ecb8fa28>7 if no value or value is wrong in the dictionary: print operator["("] (3,4) Error such as:traceback  (Most recent call last):           File  "switch.py", line 20, in <module>             print operator["(3,4)         KeyError:  ' (' So we can use the Get method in the dictionary:traceback  (most recent call last):  print operator.get["-"] (3,4 )   File  "switch.py", line 21, in <module>     print operator.get["-"] (3,4) typeerror:  ' Builtin_function_or_method '  object is  Unsubscriptable

Implement the same operation as if:

[email protected] tools]# cat switch.py
#!/usr/bin/python
#coding: Utf-8
From __future__ Import Division

def Jia (x, y):
Return X+y

Def Jian (x, y):
return x-y

def chu (x, y):
return x/Y

Def cheng (x, y):
Return X*y

operator = {"+": Jia, "-": Jian, "*": Cheng, "/": Chu}
def f (x,o,y):
Print Operator.get (o) (x, y) #将字典中的key带入函数中 similar to the If judgment
F (2, "-", 4)
[email protected] tools]# python switch.py
-2

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Python Basic Learning switch statement