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How to Implement Switch Case Functions in Python? [2022]

Rohit Sharma is the Program Director for the UpGrad-IIIT Bangalore, PG Diploma Data Analytics Program.

Jan 8, 2021
Home > Data Science > How to Implement Switch Case Functions in Python? [2022]

Introduction

Have you ever wondered if there is an alternative to write those complex If-else statements in Python? If you do not want multiple ‘If’ statements to clutter your code, you should consider using the Switch case statement that provides a cleaner and quicker way to implement control flow in your code. Unlike C++, Java, Ruby, and other programming languages, Python does not provide a switch case statement, but it offers few workarounds to make this statement work.

For example, Python allows you to create your code snippets that work like Python Switch case statements in the other programming languages. You will get to know more about the ways of implementing switch-case statements later in this blog. If you are interested to learn more about python, check out our data science courses.

What is a Switch Statement in Python?

In general, the switch is a control mechanism that tests the value stored in a variable and executes the corresponding case statements. Switch case statement introduces control flow in your program and ensures that your code is not cluttered by multiple ‘if’ statements.

Hence, your code looks meticulous and transparent to viewers. It is a wonderful programming feature that programmers use to implement the control flow in their code. Switch case statement works by comparing the values specified in the case statements with variables in your code. 

How to Implement Python Switch Case Statement

If you have always coded in languages like C++ or Java, you may find it odd that Python does not have a switch case statement. Instead, Python offers numerous workarounds like a dictionary, Python classes, or Python lambda functions to implement switch-case statements. 

If you want to know the exact reason behind not having a switch case statement in python, then you should check PEP 3103. 

Before diving deep into these alternatives, let us first see how a switch case function typically works in other programming languages.

In the below example, we have used the C programming language

switch (monthOfYear) {

    case 1:

        printf(“%s”, January);

        break;

    case 2:

        printf(“%s”, February);

        break;

    case 3:

        printf(“%s”, March);

        break;

    case 4:

        printf(“%s”, April);

        break;

    case 5:

        printf(“%s”, May);

        break;

    case 6:

        printf(“%s”, June);

        break;

    case 7:

        printf(“%s”, July);

        break;

   case 8:

        printf(“%s”, August);

        break;

    case 9:

        printf(“%s”, September);

        break;

    case 10:

        printf(“%s”, October);

        break;

    case 11:

        printf(“%s”, November);

        break;

    case 12:

        printf(“%s”, December);

        break;

    default:

        printf(“Incorrect month”);

        break;

    }

Now, let us go further into Python switch case function alternatives and understand how these alternatives work with the help of examples.

Read: Career Opportunities in Python: Everything You Need To Know

Using Dictionary Mapping

If you are familiar with other programming languages, then you must be knowing that the dictionary uses key-value pairs to store a group of objects in memory. When you are using a dictionary as an alternative to switch-case statements, keys of the key-value pair work as a case. 

The following example shows the implementation of the switch case statement using a dictionary. Here, we are defining a function month() to print which month, a month of the year is.

First, start by creating case statements and write individual functions for each case. Make sure that you write a function that tackles the default case.

def january():

    return “January”

def february():

    return “February”

def march():

    return “march”

def april():

    return “April”

def may():

    return “may”

def june():

    return “June”

def july():

    return “July”

def august():

    return “august”

def september():

    return “September”

def october():

    return “October”

def november():

    return “November” 

def december():

    return “December”

def default():

    return “Incorrect month”

Next, create a dictionary object in Python and store all the functions that you have defined in your program.

switcher = {

    0: ‘january’,

    1: ‘february’,

    2: ‘march’,

    3: ‘april’,

    4: ‘may’,

    5: ‘june’,

    6: ‘july’,

    7: ‘august’,

    8: ‘september’,

    9: ‘october’,

    10: ‘november’,

    11: ‘december’

    }

Lastly, create a switch function in your program that should accept integer as an input, performs a dictionary lookup, and invokes the corresponding functions.

def month(monthOfYear):

    return switcher.get(monthOfYear, default)()

The complete code will look like this

def january():

    return “January”

def february():

    return “February”

def march():

    return “march”

def april():

    return “April”

def may():

    return “may”

def june():

    return “June”

def july():

    return “July”

def august():

    return “august”

def september():

    return “September”

def october():

    return “October”

def november():

    return “November” 

def december():

    return “December”

def default():

    return “Incorrect month”

    

switcher = {

    0: ‘january’,

    1: ‘february’,

    2: ‘march’,

    3: ‘april’,

    4: ‘may’,

    5: ‘june’,

    6: ‘july’,

    7: ‘august’,

    8: ‘september’,

    9: ‘october’,

    10: ‘november’,

    11: ‘december’

    }

def month(monthOfYear):

    return switcher.get(monthOfYear, default)()

print(switch(1))

print(switch(0))

The above code prints the following output

February

January

Also Read: 42 Exciting Python Project Ideas & Topics for Beginners

Using Python Classes

You can also use Python classes as an alternative to implementing switch-case statements. A class is an object constructor that has properties and methods. Let us understand this further with the help of the same above example. Here, we will define a switch method inside a Python switch class.

Example

First, we will define a switch method inside a Python switch class that takes a month of the year as an argument, converts the result into a string.  

class PythonSwitch:

    def month(self, monthOf Year):

        default = “Incorrect month”

        return getattr(self, ‘case_’ + str(monthOf Year), lambda: default)()

Note: In the above example, we have used two things: keyword lambda and getattr() method. 

  • We use the lambda keyword to define an anonymous function in Python. Lambda keyword invokes the default function when a user enters invalid input.
  • getattr() method is used to invoke a function in Python.

Now, create individual functions for each case.

def january(self):

        return “January”

 

    def february(self):

        return “February”

   def march(self):

        return “March”

   

   def april(self):

        return “April”

 

    def may(self):

        return “May”

 

    def june(self):

        return “June”

   def july(self):

        return “July”

 

    def august(self):

        return “August”

 

    def september(self):

        return “September”

   def october(self):

        return “October”

 

    def november(self):

        return “November”

 

    def december(self):

        return “December”

The complete code will look like this

class PythonSwitch:

    def month(self, monthOf Year):

        default = “Incorrect month”

        return getattr(self, ‘case_’ + str(monthOf Year), lambda: default)()

    def january(self):

        return “January”

 

    def february(self):

        return “February”

 

    def march(self):

        return “March”

   

   def april(self):

        return “April”

 

    def may(self):

        return “May”

 

    def june(self):

        return “June”

   def july(self):

        return “July”

 

    def august(self):

        return “August”

 

    def september(self):

        return “September”

   def october(self):

        return “October”

 

    def november(self):

        return “November”

 

    def december(self):

        return “December”

my_switch = PythonSwitch()

print (my_switch.month(1))

print (my_switch.month(10))

The above code prints the following output

January

October

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Conclusion

In this blog, you have learned about switch-case statements, what are the alternatives of switch-case statements, and how to use them. As explained above, Python does not have an in-built switch case function, but you can always use these alternatives to make your code look neat and clean and get better performance. 

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Differentiate between an ordinary dictionary and a Python dictionary.

Python Dictionary or “Dict” is an inbuilt data structure of Python that is used to store an unordered collection of elements. Unlike other Python data structures that store single values, the dictionary data structure stores key-value pairs where every key is unique. It does not remember the insertion order of key-value pairs and iterates through the keys. On the other hand, an Ordered Dictionary or OrderedDict keeps a track of the insertion order of key-value pairs. It also consumes more memory than a regular dictionary in Python due to its doubly linked list implementation. If you delete and re-insert the same key, it will be inserted in its original position as an OrderedDict remembers the insertion order.

What operations of namedtuple make it a convenient option to be used for switch cases?

The namedtuple in Python performs various operations. The following is a list of some of the most common operations performed by the namedtuple. The elements in a namedtuple can be accessed by their indices, unlike a dictionary. The alternative way to access the elements is by their key name. The make() function returns a namedtuple. The _asadict() function returns an ordered dictionary that is constructed from the mapped values. The _replace() function takes a key name as its argument and changes the values mapped to it. The _fileds() function returns all the key names of the given namedtuple.

When do we prefer lists for storing data?

Python list is considered to be the best data structure to store the data in the following scenarios - A list can be used to store various values with different data types and can be accessed just by their respective indices. When you need to perform mathematical operations over the elements, a list can be used since it allows you to mathematically operate the elements directly. Since a list can be resized, it can be used to store the data when you are not certain about the number of elements to be stored. The list elements are easily mutable and it can also store duplicate elements, unlike set and dictionary.

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