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Tuples

Code sample link: https://replit.com/@jjoco/python-tuples

Tuples, like lists, contain a record of values. Unlike lists, however, tuples cannot be changed after they have been created; you cannot remove or add more elements into a tuple.

Why use tuples

When we know what values are going to be in collection, it is generally better to use tuples than lists. Tuples are also generally faster and memory efficient to create and read than lists since tuples have constant size. Unlike lists, in which it is almost mandatory practice to have lists contain only one data type, it is an okay practice to have multiple types in a tuple. This is why each element in a dictionary.items() call is a 2-tuple, in which the key and value types may not coincide.

So, if you wanted to maintain a running list of users with fields age, name, and id, you may not need to create a separate class for User. The list can look something like 

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[(25, "justin", 0), (38, "jack", 1), (35, "jackie", 2)]
Since we know that the size of the tuples are constant, we can more easily process them.

Creating a tuple

You can create a tuple using parentheses () like so: 

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empty_tuple = ()
packed_tuple = (2, 5 , 7, 3, 2, 1, 9)
Keep in mind that if you make an empty tuple, you will not be able to change it.

Accessing a tuple element

Like lists, you can access a value or group of values via indexing: 

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print(packed_tuple[1])

print(packed_tuple[1:5])

Getting the length of a tuple

To get the number of elements in a tuple (ie. its length), use the len function: 

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tuple_length = len(my_tuple)
So, if my_tuple = (2, True, False, "hello"), then len(my_tuple) would be 4.

Unpacking a tuple

Though it is not as common for lists and dictionaries to be unpacked, unpacking a tuple (ie assigning values within the tuple to external variables) is much more common due to its immutability: 

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date_tuple = ("04", "05", "2019")

(month, day, year) = date_tuple
print(month) 
print(day) 
print(year) 
'''
Prints out:
04
05
2019
'''
To continue on the example from before about a user_list, we can use unpacking to more easily process the user list: 
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user_list = [(25, "justin", 0), (38, "jack", 1), (35, "jackie", 2)]
for age, name, id in user_list:
  print(age)
  print(name)
  print(id)
  print()
'''
Prints out:
25
justin
0

38
jack
1

35
jackie
2
'''
Here, we unpack all three elements of the 3-tuple and can process them separately.

Recall that when we process a dictionary's items using dictionary.items(), we use syntax: 

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for some_key, some_val in some_map.items():
    .
    .
    .
This shows that the return value of .items() is a list of 2-tuples, and we're unpacking each 2-tuple item into some_key and some_val.