5 ways to implement Python Switch Case statement

In this article, I will take you through the five ways to implement the Python Switch Case statement.

A switch case statement in a computer programming language is a powerful tool that gives the total programmer control over the program’s flow according to an expression’s outcomes or a variable.

Switch cases are mainly used to execute a different block of codes in relation o the results of expression during the program run time.

The program takes a particular course if the result is an absolute value and another course if the result is another value.

Let me begin by showing you how a switch case statement functions in Java development so that you know what to expect in the python switch case statement; although it could be different in the way they have implemented, the concept remains the same.

Let’s see the Java switch case demo of switching between months of the year and providing a default result if no match is found in the switch statement.

public static void switch_demo(String[] args) {

  int month = 7;

  String monthString;

  switch (month) {

  case 1:
    monthString = "January";

    break;

  case 2:
    monthString = "February";

    break;

  case 3:
    monthString = "March";

    break;

  case 4:
    monthString = "April";

    break;

  case 5:
    monthString = "May";

    break;

  case 6:
    monthString = "June";

    break;

  case 7:
    monthString = "July";

    break;

  case 8:
    monthString = "August";

    break;

  case 9:
    monthString = "September";

    break;

  case 10:
    monthString = "October";

    break;

  case 11:
    monthString = "November";

    break;

  case 12:
    monthString = "December";

    break;

  default:
    monthString = "Invalid month";

    break;

  }

  System.out.println(monthString);

}

Let’s break down the above switch case statement:

• Step 1: The compiler first generates a jump table for the switch statement
• Step 2: The switch statement evaluates the variable or the expression only once.
• Step 3: The switch statement looks upon the evaluated result and makes a decision based on the result on which block of code to execute.

The default code will be executed in case there is no match found.

In the case example above, if the default block of code is executed the result will be invalid month, but since the month variable is initialized as 7, the output will be July.

Python Switch case statement examples

Python doesn’t have built-in switch statements like you could find programming languages like PHP and Java does, instead, as a Python programmer you could be tempted to use if-else-if blocks, but switch cases are efficient to use because of jump table than the if-else-if ladder.

The reason for this is, instead of evaluating each condition in a sequential manner, it looks at the evaluated expression or variable and jumps directly to the relevant branch of code to execute.

Example 1 – Switch using an if-else-if ladder

def switch():
    option = int(input("enter your option from 1-3 to get the name on month : "))

    if option == 1:
        result = "January"
        print("the month is = ",result)
 
    elif option == 2:
        result =  "febuary"
        print("the month is ", result)
 
    elif option == 3:
        result = "march"
        print("the month is ", result)
 
    else:
        print("Incorrect option")
 
 
 
switch()

In the Python switch case example above, if we input 1, January will be printed in the console; if the input is 2, February is printed. Else if the input is 3 march will be printed, else it will print the incorrect option.

Example 2 – Switch case statement using class to convert literal to string ‘month’

class PythonSwitchStatement:
 
    def switch(self, month):
        default = "Incorrect month"
        return getattr(self, 'case_' + str(month), lambda: default)()
 
    def case_1(self):
        return "January"
 
    def case_2(self):
        return "February"
 
    def case_3(self):
        return "March"
 
    def case_4(self):
        return "April"
 
    def case_5(self):
        return "May"
 
    def case_6(self):
        return "June"
    def case_7(self):
        return "July"
 
s = PythonSwitchStatement()
 
print(s.switch(3))
print(s.switch(4))
print(s.switch(10))

The output will be:

march

april

Invalid month

In the Switch Case example above First, create a class called PythonSwitchStatement to define a switch() method. It also defines other functions for specific different cases.

The switch() method takes an argument ‘month’ and converts it to string then appends it to the case literal and then passes it to the getattr() method, which then returns the matching function available in the class.

If it doesn’t find a match, the getattr() method will return lambda function as the default.

Example 3 – Dictionary mapping replacement

def numbers_to_strings(argument):

 switcher = {

0: "zero",

1: "one",

2: "two",

}

 return switcher.get(argument, "nothing")

# Driver program

if __name__ == "__main__":

 argument=1

print(numbers_to_strings(argument))

In the Python switch case example above, first, we write a function to convert a number into a string. the get() method of dictionary data type returns the value of passed argument if it is present in the dictionary. Otherwise, the second argument will be assigned as the default value of the given argument

Example 4 – using a dictionary mapping to return value

b ={

'a' : 122,

'b' : 123,

'c' : 124,

'd' : 125

}


inp = input('input a character : ')

print('The result for inp is : ', b.get(inp, -1))

Output:

input a character : b
The result for inp is :  123

In the Python Switch Case example, above we take the user input to print our result; also, the -1 is the default value if there are no keys that match the information.

Example 5 – Using dictionary mapping to switch the days of the week

def week(i):

 switcher={

0:'Sunday',

1:'Monday',

2:'Tuesday',

3:'Wednesday',

4:'Thursday',

5:'Friday',

6:'Saturday'

}
 return switcher.get(i, "Invalid day of the week")

This make calls to week() with different values to find out the day of the week.

i.e  week(2), the output will be Tuesday, week(4), the output will be Thursday while week(5.5) will output “Invalid day of the week”

Conclusion

Python does not have an in-built switch-case construct, but you can use dictionary mapping instead of the switch case.

Python developer did not include the switch-case construct for a good reason.

Although many programmers and developers have been pushing for the inclusion of switch case constructs in Python, whether their proposal will be considered, Python switch case alternatives serve even better.