Switch case with 3 variables

Question

can I write a switch/case statement with three variables to replace this code :

 if where_clause == 0:
   requete(liste_fields,schema,table)
 elif where_clause == 1:
   if like_clause == 0:
     if any_clause == 1:
        requete_where_any(liste_fields,schema,table,wc_1,any_1)
     else:
        requete_where(liste_fields,schema,table,wc_1,wc_2)
   elif like_clause == 1:
        requete_like(liste_fields,schema,table,like_1,like_2)
 elif where_clause == 2:
        requete_double_where(liste_fields,schema,table,wc_1,wc_2,wc_3,wc_4)
 elif where_clause == 3:
        requete_triple_or(liste_fields,schema,table,oc_1,oc_2,oc_3,oc_4,oc_5,oc_6)

You can't put an `elif` after an `else`. Perhaps an indentation error? — Tom Karzes, May 16 '20 at 23:51
Check this out: https://stackoverflow.com/questions/60208/replacements-for-switch-statement-in-python — Mayank Porwal, May 16 '20 at 23:51

angeldeluz777 · Answer 1 · 2020-05-17T03:51:50.327

I made a switch class. It is initialized with the value, a dict where the key, value pairs represent the actions for each value as a list containing a function and optional parameters and an optional default action. For example you should call it like this:

sw = switch(some_value, 
     {
         1:[print, 'hello'], 
         2:[print, 'goodby']
     },
     default=[print])

Tthe default argument has no parameters, so just print a new line.

The corresponding function is called when the switch is called:

sw()

The good thing is that as a switch object has a __call__ method, switches can be nested.

Here is the implementation and the application for your case:

class switch(dict):
    def __init__(self, value, cases, default = ((lambda:None),)):
        super().__init__(cases)
        self.default = default
        self.value = value

    def __call__(self):
        do = self.get(self.value, self.default)
        return do[0](*do[1:])

sw = switch(where_clause, 
     {
        0: [requete],
        1: [switch(like_clause, 
            {   
                0: [switch(any_clause, 
                   {   
                       1: [requete_where_any,liste_fields,schema,table, wc_1, any_1]
                   },  
                   default=[requete_where,liste_fields,schema,table, wc_1, wc_2])],

                1: [requete_like,liste_fields,schema,table, like_1, like_2]
            },  
            default=[requete_like,liste_fields,schema,table, like_1, like_2])],

        2: [requete_double_where,liste_fields,schema,table, wc_1, wc_2, wc_3, wc_4),
        3: [requete_triple_or,liste_fields,schema,table, oc_1, oc_2, oc_3, oc_4]    
     })

sw()

The class could be easily improved having the option to not pass a value at initialization, and to pass a value at call time, so for example:

sw = switch( 
     {
         1:[print, 'hello'], 
         2:[print, 'goodby']
     })
sw(1)  # -> 'hello'
sw(2)  # -> 'goodby'

score 1 · Accepted Answer · answered Jan 15 '21 at 03:31

You can simulate a switch statement using the following function definition:

def switch(v): yield lambda *c:v in c

Your code could then look like this:

for case in switch(where_clause):

    if case(0):
       requete(liste_fields,schema,table)
       break

    if case(1):
       for case in switch(like_clause): 
           if case(0):
               if any_clause == 1:
                   requete_where_any(liste_fields,schema,table,wc_1,any_1)
               else:
                   requete_where(liste_fields,schema,table,wc_1,wc_2)
               break

           if case(1):
               requete_like(liste_fields,schema,table,like_1,like_2)
      break
    
   if case(2):
      requete_double_where(liste_fields,schema,table,wc_1,wc_2,wc_3,wc_4)
      break

   if case(3):      
      requete_triple_or(liste_fields,schema,table, oc_1,oc_2,oc_3,oc_4,oc_5,oc_6)
      break

Note that tyou don't have to use the word case, you can pick something more meaningful:

for where in switch(where_clause):

    if where(0):
       requete(liste_fields,schema,table)
       break

    if where(1):
       for like in switch(like_clause): 
           if like(0):
               if any_clause == 1:
                   requete_where_any(liste_fields,schema,table,wc_1,any_1)
               else:
                   requete_where(liste_fields,schema,table,wc_1,wc_2)
               break

           if like(1):
               requete_like(liste_fields,schema,table,like_1,like_2)
      break
    
   if where(2):
      requete_double_where(liste_fields,schema,table,wc_1,wc_2,wc_3,wc_4)
      break

   if where(3):      
      requete_triple_or(liste_fields,schema,table, oc_1,oc_2,oc_3,oc_4,oc_5,oc_6)
      break

Switch case with 3 variables

2 Answers2