A switch statement for Python

Blog A switch statement for Python
Posted on Jun 13, 2012 by Caleb Thorne

Many languages support a control structure called the switch statement that is an alternative for if/else-if. Python, however, has no switch statement. Does that mean we must always resort to using a sequence of if/elif? Not necessarily!

Python uses one of the most efficient hashing algorithms for it’s dictionary type. We can use a dictionary to create a type of switch statement that is both efficient and very elegant. Consider the following sequence of if/elif to find a holiday for a given month.

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30 month = 'March'

if month.lower() == "january":
  holiday = "New Year"
if month.lower() == "february":
  holiday = "Valentine's Day"
elif month.lower() == "march":
  holiday = "St. Patrick's Day"
elif month.lower() == "april":
  holiday = "Easter"
elif month.lower() == "may":
  holiday = "Mother's Day"
elif month.lower() == "june":
  holiday = "Father's Day"
elif month.lower() == "july":
  holiday = "Independence Day"
elif month.lower() == "august":
  holiday = "Lemonade Stand Day"
elif month.lower() == "september":
  holiday = "Labor Day"
elif month.lower() == "october":
  holiday = "Holloween"
elif month.lower() == "november":
  holiday = "Thanksgiving"
elif month.lower() == "december":
  holiday = "Christmas"
else:
  holiday = "Error: Invalid month!"

print holiday

This can be made much more readable and pythonic by using a dictionary.

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15 month = 'March'
holiday = {"january":"New Year",
           "february":"Valentine's Day"
           "march":"St. Patrick's Day"
           "april":"Easter"
           "may":"Mother's Day"
           "june":"Father's Day"
           "july":"Independence Day"
           "august":"Lemonade Stand Day"
           "september":"Labor Day"
           "october":"Holloween"
           "november":"Thanksgiving"
           "december":"Christmas"}.get(month.lower(), "Error: Invalid month!")

print holiday