switch-case in python, python case writing method

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method one

Python 3.10 version has updated the switch case structure similar to other languages, so the best way is to update directly to python3.10 and use the match case statement directly:

C language:

switch (expression) {
    case constant-expression :
       statement(s);
       break; /* 可选的 */
    case constant-expression :
       statement(s);
       break; /* 可选的 */
    /* 您可以有任意数量的 case 语句 */
    default : /* 可选的 */
       statement(s);
}

Python：

flag = False
match (100, 200):
   case (100, 300):  # Mismatch: 200 != 300
       print('Case 1')
   case (100, 200) if flag:  # Successful match, but guard fails
       print('Case 2')
   case (100, y):  # Matches and binds y to 200
       print(f'Case 3, y: {y}')
   case _:  # Pattern not attempted
       print('Case 4, I match anything!')

#PEP 634: Structural Pattern Matching
match subject:
    case <pattern_1>:
        <action_1>
    case <pattern_2>:
        <action_2>
    case <pattern_3>:
        <action_3>
    case _:
        <action_wildcard>

A more detailed introduction:
[Python] Python 3.10 new features match case statement_python match case_AiFool's blog-CSDN blog

Method 2

Use functions to achieve effects similar to switch cases:

def switch_case(value):
    switcher = {
        0: "zero",
        1: "one",
        2: "two",
    }
     
    return switcher.get(value, 'wrong value')

Implemented using anonymous functions:

def foo(var,x):
	return {
			'a': lambda x: x+1,
			'b': lambda x: x+2,
			'c': lambda x: x+3,	
	}[var](x)

Method three

Custom switch case class:

# This class provides the functionality we want. You only need to look at
# this if you want to know how this works. It only needs to be defined
# once, no need to muck around with its internals.
class switch(object):
	def __init__(self, value):
    	self.value = value
    	self.fall = False

	def __iter__(self):
    	"""Return the match method once, then stop"""
    	yield self.match
    	raise StopIteration

    def match(self, *args):
        """Indicate whether or not to enter a case suite"""
        if self.fall or not args:
            return True
        elif self.value in args: # changed for v1.5, see below
            self.fall = True
            return True
        else:
            return False


# The following example is pretty much the exact use-case of a dictionary,
# but is included for its simplicity. Note that you can include statements
# in each suite.
v = 'ten'
for case in switch(v):
    if case('one'):
        print 1
        break
    if case('two'):
        print 2
        break
    if case('ten'):
        print 10
        break
    if case('eleven'):
        print 11
        break
    if case(): # default, could also just omit condition or 'if True'
        print "something else!"
        # No need to break here, it'll stop anyway

# break is used here to look as much like the real thing as possible, but
# elif is generally just as good and more concise.

# Empty suites are considered syntax errors, so intentional fall-throughs
# should contain 'pass'
c = 'z'
for case in switch(c):
    if case('a'): pass # only necessary if the rest of the suite is empty
    if case('b'): pass
    # ...
    if case('y'): pass
    if case('z'):
        print "c is lowercase!"
        break
    if case('A'): pass
    # ...
    if case('Z'):
        print "c is uppercase!"
        break
    if case(): # default
        print "I dunno what c was!"

# As suggested by Pierre Quentel, you can even expand upon the
# functionality of the classic 'case' statement by matching multiple
# cases in a single shot. This greatly benefits operations such as the
# uppercase/lowercase example above:
import string
c = 'A'
for case in switch(c):
    if case(*string.lowercase): # note the * for unpacking as arguments
        print "c is lowercase!"
        break
    if case(*string.uppercase):
        print "c is uppercase!"
        break
    if case('!', '?', '.'): # normal argument passing style also applies
        print "c is a sentence terminator!"
        break
    if case(): # default
        print "I dunno what c was!"

# Since Pierre's suggestion is backward-compatible with the original recipe,
# I have made the necessary modification to allow for the above usage.

Reference: https://www.cnblogs.com/gerrydeng/p/7191927.html