Switch Case in Python

An efficient dictionary mapping, also known as associative arrays, is a pythonic way of implementing a switch-statement that offers one-to-one key-value mappings. Follow the below steps.

1.First, creating separate function for each case and make sure there is a default case to handling function.

def monday():
    return "monday"
def tuesday():
    return "tuesday"
def wednesday():
    return "wednesday"
def thursday():
    return "thursday"
def friday():
    return "friday"
def saturday():
    return "saturday"
def sunday():
    return "sunday"
def default():
    return "Invalid day"

2. Next, build a dictionary object(It store key-value pair in the memory) and save each function.

switcher = {
    1: monday,
    2: tuesday,
    3: wednesday,
    4: thursday,
    5: friday,
    6: saturday,
    7: sunday
}

3 Write a switch() function that accepts the day of the week as an argument.

def switch(dayOfWeek):
    return switcher.get(dayOfWeek, default)()

4 Switch() calls the get() method on the dictionary object, which returns and concurrently invokes function that match the argument.

print(switch(1))
print(switch(0))

Example: Implement Python Switch Case Statement using Dictionary

def monday():
    return "monday"
def tuesday():
    return "tuesday"
def wednesday():
    return "wednesday"
def thursday():
    return "thursday"
def friday():
    return "friday"
def saturday():
    return "saturday"
def sunday():
    return "sunday"
def default():
    return "Invalid day"
switcher = {
    1: monday,
    2: tuesday,
    3: wednesday,
    4: thursday,
    5: friday,
    6: saturday,
    7: sunday
}
def switch(dayOfWeek):
    return switcher.get(dayOfWeek, default)()
print(switch(1))
print(switch(0))

The output is as follows:

Monday
Invalid day

Here when we pass an argument to the switch function, the switcher’s dictionary mapping is scanned. The associated value is printed if a match is found. Otherwise, a default string ('Invalid day') is printed. The default string helps to implement the switch 'default case.'

Switch Case using a Class

Python classes may also be used as an alternate way to execute switch-case statements. Let’s use an example to do so.

• First, There is a switch class, which specifies the switch() method.
• The day of the week is an argument, it is converted to a string, and it is appended to the 'case_ ' literal. The resulting string is then passed to the getattr() function.
• The getattr() method returns the matching function of the type.
• If the string doesn’t find a match, getattr() returns the default lambda function.

# Implement Python Switch Case Statement using Class
class Switch:
   def switch(self, dayOfWeek):
       default = "Invalid day"
       return getattr(self, 'case_' + str(dayOfWeek), lambda: default)()
   def case_1(self):
       return "Monday"
   def case_2(self):
       return "Tuesday"
   def case_3(self):
       return "Wednesday"
s = Switch()
print(s.switch(1))
print(s.switch(0))

The output is as follows:

Monday
Invalid day

Switch Case using Python functions

The Python dictionary values may be of any data. Therefore, we don’t have to use constants (integers, strings). Function names and lambdas may also be used as values.

E.g., by building a dictionary of function names as values, we can also implement this switch statement. It is convenient to use with the Python switch case statement. We have a few steps to consider.

• First, for each case, specify the individual functions.
• Make sure there is a default case handling function.
• First, create a dictionary object and store each of the functions.
• After that, write a switch() function that accepts the number of months as arguments.
• The switch() calls a get() method on a dictionary object that returns and concurrently calls a function matching the argument.
In this case, a switcher is a function names dictionary without strings.

def monday():
    return "monday"
def tuesday():
    return "tuesday"
def wednesday():
    return "wednesday"
def thursday():
    return "thursday"
def friday():
    return "friday"
def saturday():
    return "saturday"
def sunday():
    return "sunday"
def switch(dayOfWeek):
switcher = {
    1: monday,
    2: tuesday,
    3: wednesday,
    4: thursday,
    5: friday,
    6: saturday,
    7: sunday
}
    func = switcher.get(dayOfWeek, lambda: "Invalid day")
    print func()