What are sets in Python?
What is a set?
A set is an unordered and unindexed “bag” of unique values.
A single set can contain values of any immutable datatype which means the values can’t be changed. A set itself is a mutable object i.e, an object that can be changed after it is created.
Creating a set
Let’s learn how to create a set.
a_set = {'alpha', 'bravo', 'charlie'}print (a_set)#A set can also be created using the built-in set() function#set() takes a "list" as argument and converts it to a setmy_set = set([1,2,3,4,5])print (my_set)
Accessing items
Sets are unindexed, hence you cannot access items in a set by referring to an index. What you can do is loop through the set in order to get a specific value.
a_set = {'alpha', 'bravo', 'charlie'}for item in a_set:print (item)
Note: Sets are unordered, so the items will appear in a random order.
Methods
Python has a set of built-in methods that you can use on sets. Some of them are specified below:
-
Add items: Once a set is created, you cannot change its items, but you can add new items. To add one item to a set, use the
add()method and to add more than one item to a set, use theupdate()method. -
Remove items: To remove an item in a set, use the
remove()method. You can also use thediscard()method for removing.
a_set = {'alpha', 'bravo', 'charlie'}print ("Adding value to set")a_set.add('jenny')print(a_set)a_set.update(['matty', 'johny'])print ("Updating values in set")print(a_set)print ("Removing value from set")a_set.remove('matty') #If the item to remove does not exist, `remove()` will raise an error.print(a_set)print ("Discarding value from set")a_set.discard('johny') #If the item to remove does not exist, `discard()` will **NOT** raise an error.print(a_set)
-
Length of set: The
len()method can be used to determine the count of items in a set. -
Clear set: The
clear()method empties the set.
a_set = {'alpha', 'bravo', 'charlie'}print ("Number of items are: ", (len(a_set)))a_set.clear()print("set cleared")print(a_set)
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