{"id":4014,"date":"2017-10-26T02:07:48","date_gmt":"2017-10-26T02:07:48","guid":{"rendered":"http:\/\/www.jquery-az.com\/?p=4014"},"modified":"2023-04-05T21:00:44","modified_gmt":"2023-04-05T21:00:44","slug":"2-python-switch-case-default-statement-alternatives-get-solutions","status":"publish","type":"post","link":"https:\/\/www.jquery-az.com\/2-python-switch-case-default-statement-alternatives-get-solutions\/","title":{"rendered":"The Python switch case statement?"},"content":{"rendered":"

The switch case is a decision-making statement that enables switching on a single variable where that variable may have one or multiple possible values. The switch statement is available in many programming languages including Java<\/a>, PHP<\/a>, JavaScript<\/a> etc.<\/p>\n

However, Python has no switch case statement. The proposal for switching on multiple values using switch\/case was rejected.<\/p>\n

The question is what is the alternative? As such, the scenarios will come where you need the switch case usage as doing programming in Python.<\/p>\n

The official site<\/a> suggests using the if\u2026elif\u2026elif..else statements<\/a> for the limited number of possibilities (say up to 12 or so). However, for a very large number of possibilities, you may create a dictionary.<\/p>\n

In that case, the dictionary will map the case values to functions call. I will show the running example with code in the coming section.<\/p>\n

First alternative \u2013 using the dictionary <\/strong><\/h3>\n

As mentioned in the official documentation, you should use the dictionary mapping case values to functions call.<\/p>\n

This is demonstrated in the demo below. The scenario is to get the current month from the system and display a respective message to the screen. As\u00a0there are only twelve possibilities, so 12 \u201ccases\u201d are created i.e. one function for each month.<\/p>\n

The current month value is getting by using the datetime module and this is how the dictionary is mapped with case values.<\/p>\n

Python program:<\/strong><\/p>\n

import datetime\r\n\r\ncurr_Month =\u00a0 datetime.date.today().strftime(\"%B\")\r\n\r\n\r\n\r\n#Functionas are created for each case\r\n\r\ndef Jan ():\r\n\r\n\u00a0\u00a0 print(\"January - Starting new Year\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Feb ():\r\n\r\n\u00a0\u00a0 print(\"February - The Second Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Mar ():\r\n\r\n\u00a0\u00a0 print(\"March - The Third Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Apr ():\r\n\r\n\u00a0\u00a0 print(\"April - The Fourth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef May ():\r\n\r\n\u00a0\u00a0 print(\"May - The Fifth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Jun ():\r\n\r\n\u00a0\u00a0 print(\"June - The Sixth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Jul ():\r\n\r\n\u00a0\u00a0 print(\"July - The Seventh Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Aug ():\r\n\r\n\u00a0\u00a0 print(\"August - The Eighth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Sep ():\r\n\r\n\u00a0\u00a0 print(\"September - The Ninth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Oct ():\r\n\r\n\u00a0\u00a0 print(\"October - The Tenth Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Nov ():\r\n\r\n\u00a0\u00a0 print(\"November - The Eleventh Month\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Dec ():\r\n\r\n\u00a0\u00a0 print(\"December - The End of Year\")\r\n\r\n\r\n\r\n#Dictionary containing all possible values\r\n\r\nMonth_Dict = {\r\n\r\n\u00a0\u00a0\u00a0 \"January\": Jan,\r\n\r\n\u00a0\u00a0\u00a0 \"February\": Feb,\r\n\r\n\u00a0\u00a0\u00a0 \"March\": Mar,\r\n\r\n\u00a0\u00a0\u00a0 \"April\": Apr,\r\n\r\n\u00a0\u00a0\u00a0 \"May\": May,\r\n\r\n\u00a0\u00a0\u00a0 \"June\": Jun,\r\n\r\n\u00a0\u00a0\u00a0 \"July\": Jul,\r\n\r\n\u00a0\u00a0\u00a0 \"August\": Aug,\r\n\r\n\u00a0\u00a0\u00a0 \"September\": Sep,\r\n\r\n\u00a0\u00a0\u00a0 \"October\": Oct,\r\n\r\n\u00a0\u00a0\u00a0 \"November\": Nov,\r\n\r\n\u00a0\u00a0\u00a0 \"December\": Dec\u00a0\u00a0\u00a0\r\n\r\n\u00a0\u00a0\u00a0 }\r\n\r\n\r\n\r\n#The switch alternative\r\n\r\nMonth_Dict.get(curr_Month)()<\/pre>\n
Output:<\/strong><\/p>\n
\"switch<\/p>\n
So, the curr_Month is assigned the system value for Month by using datetime.date.today().strftime(“%B”)<\/em><\/strong>. This is passed to the dictionary get method that is mapped to a function call.<\/p>\n
 <\/p>\n
What if a case value is non-existent \u2013 the default statement?<\/strong><\/h3>\n
In our example of Python switch case alternative, we used Month value that we got by using the time module. So, there was no possibility that a non-existent case happen.<\/p>\n
What if a value does not exist? In case of switch statement, the default case<\/strong> can be used that will execute if the provided value does not match any case.<\/p>\n
Suppose, we set the value for curr_Month variable a non-month, see what will happen to the above example:<\/p>\n
curr_Month =\u00a0 ‘No Month’<\/p><\/blockquote>\n
As you execute the above example with this value, this will be the output:<\/p>\n
\"switchSo, an error occurs. How to avoid this?<\/p>\n
Using the default \u201ccase\u201d <\/strong><\/h3>\n
To avoid the error, you may create a default function that acts as an alternative to the \u201cdefault case\u201d in the switch context. So if none of the cases matches the provided value, the default function should execute. This is demonstrated in the example below.<\/p>\n
A user is asked to enter a number from 1 to 7 by using the input function. The 1 represents Monday, 2 for Tuesday and so on. For any other entry, the default case will execute. See the code and output:<\/p>\n
#A Demo of switch case with default case\r\n\r\n\r\n\r\nday_num =\u00a0 input(\"Enter a day number from 1-7? \")\r\n\r\n\r\n\r\n#Functionas are created for each day with default case\r\n\r\ndef Mon ():\r\n\r\n\u00a0\u00a0 print(\"Its Monday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Tue ():\r\n\r\n\u00a0\u00a0 print(\"Its Tuesday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Wed ():\r\n\r\n\u00a0\u00a0 print(\"Its Wednesday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Thu ():\r\n\r\n\u00a0\u00a0 print(\"Its Thursday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Fri ():\r\n\r\n\u00a0\u00a0 print(\"Its Friday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Sat ():\r\n\r\n\u00a0\u00a0 print(\"Its Saturday\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Sun ():\r\n\r\n\u00a0\u00a0 print(\"Hurray, Its Sunday!\")\r\n\r\n\u00a0\u00a0\r\n\r\ndef Default_case ():\r\n\r\n\u00a0\u00a0 print(\"Wrong entry! The number must be 1-7\")\r\n\r\n\r\n\r\n#Dictionary containing all possible 'cases'\r\n\r\nWeek_Dict = {\r\n\r\n\u00a0\u00a0\u00a0 \"1\": Mon,\r\n\r\n\u00a0\u00a0\u00a0 \"2\": Tue,\r\n\r\n\u00a0\u00a0\u00a0 \"3\": Wed,\r\n\r\n\u00a0\u00a0\u00a0 \"4\": Thu,\r\n\r\n\u00a0\u00a0\u00a0 \"5\": Fri,\r\n\r\n\u00a0\u00a0\u00a0 \"6\": Sat,\r\n\r\n\u00a0\u00a0\u00a0 \"7\": Sun\u00a0\r\n\r\n\u00a0\u00a0 \u00a0}\r\n\r\n\r\n\r\n#The switch alternative\r\n\r\nWeek_Dict.get(day_num,Default_case)()<\/pre>\n
Sample Output:<\/strong><\/p>\n
\"Python<\/p>\n
In the output figure, you can see the last entry is 11 and it executed the default case rather than producing an error.<\/p>\n
Note: the get method of default returns the value for key if key is in the dictionary. Otherwise, it returns default.<\/em><\/p>\n
Switch alternative 2 \u2013 using if..elif..elif..else statement<\/strong><\/h3>\n
As per official recommendation, for the small number of possibilities, you may use the if..elif, elif\u2026else statements. In that case, the else acts as the “default” case in the context of the switch statement.<\/p>\n
See the above Week example by using this approach:<\/p>\n
w = \u00a0int(input(\"Enter a day number from 1-7? \"))\r\n\r\nif (w == 7): print(\"Its Sunday.\");\r\n\r\nelif<\/a> (w == 1): print(\"Monday is the the first working day!\");\r\n\r\nelif (w == 2): print(\"Tuesday!!!\");\r\n\r\nelif (w == 3): print(\"Wednesday...Getting closer!\");\r\n\r\nelif (w == 4): print(\"and mmore...its Thursday!\");\r\n\r\nelif (w == 5): print(\"Friday...Hurray! so close!\");\r\n\r\nelif (w == 6): print(\"Yay, the Weekend started, as its Sat!\");\r\n\r\nelse: print(\"Wrong entry! The number must be 1-7\");<\/pre>\n
\"switch<\/p>\n
For more on if..elif and else statements<\/a>, follow the link.<\/p>\n","protected":false},"excerpt":{"rendered":"
The official site suggests using the if\u2026elif\u2026elif..else statements for the limited number of possibilities (say up to 12 or so). However, for a very large number of possibilities, you may create a dictionary.<\/p>\n","protected":false},"author":1,"featured_media":4017,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[17],"tags":[],"yoast_head":"\n2 Python switch case \/default Statement Alternatives? Get Solutions<\/title>\n<meta name=\"description\" content=\"The if\u2026elif\u2026elif..else statements for the limited number of possibilities. 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