Python in 30 Days: Day 6 – Tuples

Day 6

Tuples

A tuple is a collection of different data types that is ordered and unchangeable (immutable). Tuples are written with round brackets, (). Once a tuple is created, we cannot change its values. We cannot use add, insert, remove methods in a tuple because it is not modifiable (mutable). Unlike list, tuple have few methods. Methods related to tuples:

• tuple(): to create an empty tuple
• count(): to count the number of a specified item in a tuple
• index(): to find the index of a specified item in a tuple
• • operator: to join two or more tuples and to create a new tuple

Creating a Tuple

• Empty tuple: Creating an empty tuple

  # syntax
  empty_tuple = ()
  # or using the tuple constructor
  empty_tuple = tuple()

• Tuple with initial values

  # syntax
  tpl = ('item1', 'item2','item3')

  fruits = ('banana', 'orange', 'mango', 'lemon')

Tuple length

We use the len() method to get the length of a tuple.

# syntax
tpl = ('item1', 'item2', 'item3')
len(tpl)

Accessing Tuple Items

• Positive Indexing Similar to the list data type we use positive or negative indexing to access tuple items. 

  # Syntax
  tpl = ('item1', 'item2', 'item3')
  first_item = tpl[0]
  second_item = tpl[1]

  fruits = ('banana', 'orange', 'mango', 'lemon')
  first_fruit = fruits[0]
  second_fruit = fruits[1]
  last_index =len(fruits) - 1
  last_fruit = fruits[las_index]

• Negative indexing means beginning from the end, -1 refers to the last item, -2 refers to the second last and the negative of the list/tuple length refers to the first item.

  # Syntax
  tpl = ('item1', 'item2', 'item3','item4')
  first_item = tpl[-4]
  second_item = tpl[-3]

  fruits = ('banana', 'orange', 'mango', 'lemon')
  first_fruit = fruits[-4]
  second_fruit = fruits[-3]
  last_fruit = fruits[-1]

Slicing tuples

We can slice out a sub-tuple by specifying a range of indexes where to start and where to end in the tuple, the return value will be a new tuple with the specified items.

• Range of Positive Indexes

  # Syntax
  tpl = ('item1', 'item2', 'item3','item4')
  all_items = tpl[0:4]         # all items
  all_items = tpl[0:]         # all items
  middle_two_items = tpl[1:3]  # does not include item at index 3

  fruits = ('banana', 'orange', 'mango', 'lemon')
  all_fruits = fruits[0:4]    # all items
  all_fruits= fruits[0:]      # all items
  orange_mango = fruits[1:3]  # doesn't include item at index 3
  orange_to_the_rest = fruits[1:]

• Range of Negative Indexes

  # Syntax
  tpl = ('item1', 'item2', 'item3','item4')
  all_items = tpl[-4:]         # all items
  middle_two_items = tpl[-3:-1]  # does not include item at index 3 (-1)

  fruits = ('banana', 'orange', 'mango', 'lemon')
  all_fruits = fruits[-4:]    # all items
  orange_mango = fruits[-3:-1]  # doesn't include item at index 3
  orange_to_the_rest = fruits[-3:]

Changing Tuples to Lists

We can change tuples to lists and lists to tuples. A tuple is immutable if we want to modify a tuple we should change it to a list.

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
lst = list(tpl)

fruits = ('banana', 'orange', 'mango', 'lemon')
fruits = list(fruits)
fruits[0] = 'apple'
print(fruits)     # ['apple', 'orange', 'mango', 'lemon']
fruits = tuple(fruits)
print(fruits)     # ('apple', 'orange', 'mango', 'lemon')

Checking an Item in a Tuple

We can check if an item exists or not in a tuple using in, it returns a boolean.

# Syntax
tpl = ('item1', 'item2', 'item3','item4')
'item2' in tpl # True

fruits = ('banana', 'orange', 'mango', 'lemon')
print('orange' in fruits) # True
print('apple' in fruits) # False
fruits[0] = 'apple' # TypeError: 'tuple' object does not support item assignment

Joining Tuples

We can join two or more tuples using the + operator

# syntax
tpl1 = ('item1', 'item2', 'item3')
tpl2 = ('item4', 'item5','item6')
tpl3 = tpl1 + tpl2

fruits = ('banana', 'orange', 'mango', 'lemon')
vegetables = ('Tomato', 'Potato', 'Cabbage','Onion', 'Carrot')
fruits_and_vegetables = fruits + vegetables

Deleting Tuples

It is not possible to remove a single item in a tuple but it is possible to delete the tuple itself using del.

# syntax
tpl1 = ('item1', 'item2', 'item3')
del tpl1

fruits = ('banana', 'orange', 'mango', 'lemon')
del fruits

 Now do some exercises for your brain and your muscles.

Exercises: Day 6

Exercises: Level 1

1. Create an empty tuple
2. Create a tuple containing the names of your sisters and your brothers (imaginary siblings are fine)
3. Join brothers and sisters’ tuples and assign it to siblings
4. How many siblings do you have?
5. Modify the sibling’s tuple add the name of your father and mother and assign it to family_members

Exercises: Level 2

1. Unpack siblings and parents from family_members
2. Create fruits, vegetables, and animal products tuples. Join the three tuples and assign it to a variable called food_stuff_tp.
3. Change the about food_stuff_tp tuple to a food_stuff_lt list
4. Slice out the middle item or items from the food_stuff_tp tuple or food_stuff_lt list.
5. Slice out the first three items and the last three items from the food_staff_lt list
6. Delete the food_staff_tp tuple completely
7. Check if an item exists in a tuple:

• Check if ‘Estonia’ is a Nordic country

• Check if ‘Iceland’ is a Nordic country

  nordic_countries = ('Denmark', 'Finland','Iceland', 'Norway', 'Sweden')

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