Python notes: Dictionary and anonymous Functions (lambda) for alternative case statements

In the Linux shell we are accustomed to use case statements to do branch processing, but Python omitted this function, after a multi-party search, found that in fact, the case statement in the C language by looking at the corresponding hash table, to jump. We can do this in Python in three ways. 1, dictionary, 2, lambda;3, switch class.

1. Dictionaries

dictcase={' case1 ': func1, ' case2 ': func2 .... ' CaseN ': FuncN}

#注意字典中对应的是函数名, no parentheses.

Use the Get function of the dictionary when calling to implement the default option:

Dictcase.get (Casen,default_func) ()

2. anonymous function lambda

Common examples on the Web:

result = {
' A ': Lambda x:x * 5,
' B ': Lambda x:x + 7,
' C ': Lambda x:x-2
}[value] (x)

I don't know much about ...

def a (s): Print sdef switch (CH): try: {' 1 ': lambda:a ("one"), ' 2 ': lambda:a ("one"), ' 3 ': lambda: A ("three"), ' a ': lambda:a ("Letter A")}[ch] () except keyerror:a ("Key not Found")

eg:


>>switch(‘1‘)
one
>>switch(‘a‘)
Letter a
>>switch(‘b‘)
Key not Found

This example is good, but the total sense of this is not very good, no dictionary flexible.

My own example:

1 #!/usr/bin/env python 2 import sys 3 4 def f1 (a): 5 Print a 6 7 def b (b): 8 Print b+1 9 g =lambda x:x #m =sys.argv[1] #n =sys.argv[2] #print m,n m=input ("functionname:") N=input ("number:") try : (m) (n) except:20 print "Function not exists:{f1,b}" 21# using a try to implement the default function

3. Install switch class: Https://pypi.python.org/pypi/switch/1.1.0#downloads

With the first two, installing this class is a bit boring ...

# -*- coding: utf-8 -*-from __future__ import with_statement__version__  =  ' 1.1.0 ' __all__ = [' cswitch ',  ' Switch ']import reclass switch (object):     class stopexecution (Exception):         pass    def __init__ (Self, switch_value, fall_through=false):         self._switch_value = switch_value         self._default_fall_through = fall_through         self._fall_through = false        self._matched_ Case = false        self._default_used = false     def __enter__ (self):        return  Self    def __exit__ (SELF, EXC_TYPE, EXC_VAL, EXC_TB):         Return exc_type is self. Stopexecution    def __call__ (Self, case_value, *case_values, **kwargs ):         return self.call (             lambda switch_value: any (switch_value == v for  v in  (case_value, )  + case_values),             **kwargs        )      def match (Self, match_value, *match_values, **kwargs):         def test (Switch_value):             # It is safe to call  ' Re.compile () '  on a Compiled pattern:            # a= Re.compile (' test ');  assert a is re.compile (a)              str_switch_value = str (Switch_value)              re_tests =  (Re.compile (v)  for v in  ( match_value, )  + match_values)              return any (Regex.match (str_switch_value)  for regex in re_tests)          return self.call (Test, **kwargs)      Def call (self, test, fall_through=none):         if  self._default_used:            raise  SyntaxError (' Case after default&nbSp;is prohibited ')         self._check_finished ()          if self._fall_through or test (Self._switch_value):             self._matched_case = True             self._fall_through = fall_through  if fall_through is not None else self._default_fall_through             return True         return False     @property     def default ( Self):         self._check_finished ()          self._default_used = true        return  not self._matched_case&nbsP;   def _check_finished (self):        if  self._matched_case is true and self._fall_through is false:             raise self. Stopexecutionclass cswitch (Switch):     "" "    cswitch is  a shortcut to call switch (test_value, fall_through=true)       "" "    def __init__ (Self, switch_value):         super (cswitch, self). __init__ (Switch_value, fall_through=true)

This article is from the "Hiubuntu" blog, make sure to keep this source http://qujunorz.blog.51cto.com/6378776/1538985