Tuples

In this lecture, you'll learn everything about Python tuples. More specifically, what are tuples, how to create them, when to use them and various methods you should be familiar with.

A tuple in Python is similar to a list. The difference between the two is that we cannot change the elements of a tuple once it is assigned whereas we can change the elements of a list.

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Creating a Tuple

A tuple is created by placing all the items (elements) inside parentheses (), separated by commas. The parentheses are optional, however, it is a good practice to use them.

A tuple can have any number of items and they may be of different types (integer, float, list, string, etc.).

# Different types of tuples
empty_tuple = ()

tuple_with_ints = (1, 2, 3)

tuple_with_floats = (1.1, 2.2, 3.3)

tuple_with_strings = ("a", "b", "c")

tuple_with_lists = ([1, 2, 3], [4, 5, 6], [7, 8, 9])

tuple_with_tuples = ((1, 2, 3), (4, 5, 6), (7, 8, 9))

mix_tuple = (1, 2.2, "a", [1, 2, 3], (1, 2, 3))

A tuple can also be created without using parentheses. This is known as tuple packing.

animals = "cat", "dog", "rabbit"

# tuple unpacking is also possible
cat, dog, rabbit = animals

print(cat) # cat
print(dog) # dog
print(rabbit) # rabbit

Creating a tuple with one element is a bit tricky.

Having one element within parentheses is not enough. We will need a trailing comma to indicate that it is, in fact, a tuple.

single_element_tuple = (1)

print(type(single_element_tuple)) # <class 'int'>

# Creating a tuple having one element
single_element_tuple = (1,)

print(type(single_element_tuple)) # <class 'tuple'>

# Parentheses is optional
single_element_tuple = 1,

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Access Tuple Elements

There are various ways in which we can access the elements of a tuple.

1. Indexing

   We can use the index operator [] to access an item in a tuple, where the index starts from 0.

   So, a tuple having 6 elements will have indices from 0 to 5. Trying to access an index outside of the tuple index range(6,7,... in this example) will raise an IndexError.

   The index must be an integer, so we cannot use float or other types. This will result in TypeError.

   Likewise, nested tuples are accessed using nested indexing, as shown in the example below.

   # Accessing tuple elements using indexing
   tuple_with_ints = (1, 2, 3)
   print(tuple_with_ints[0]) # 1
   print(tuple_with_ints[1]) # 2
   print(tuple_with_ints[2]) # 3
   
   # IndexError: list index out of range
   print(tuple_with_ints[3])
   
   # Accessing nested tuples
   tuple_with_tuples = ((1, 2, 3), (4, 5, 6), (7, 8, 9))
   print(tuple_with_tuples[0][0]) # 1
   print(tuple_with_tuples[1][1]) # 5
   print(tuple_with_tuples[2][2]) # 9

2. Negative Indexing

   Python allows negative indexing for its sequences.

   The index of -1 refers to the last item, -2 to the second last item and so on.

   # Negative indexing for accessing tuple elements
   tuple_with_ints = (1, 2, 3)
   print(tuple_with_ints[-1]) # 3

3. Slicing

   We can access a range of items in a tuple by using the slicing operator colon :.

   The start index is inclusive and the end index is exclusive.

   # Accessing a range of items in a tuple
   tuple_with_ints = (1, 2, 3, 4, 5)
   print(tuple_with_ints[1:3]) # (2, 3)
   print(tuple_with_ints[:3]) # (1, 2, 3)
   print(tuple_with_ints[3:]) # (4, 5)

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Changing a Tuple

Unlike lists, tuples are immutable.

This means that elements of a tuple cannot be changed once they have been assigned. But, if the element is itself a mutable data type like a list, its nested items can be changed.

We can also assign a tuple to different values (reassignment).

# Changing tuple values
my_tuple = (4, 2, 3, [6, 5])


# TypeError: 'tuple' object does not support item assignment
# my_tuple[1] = 9

# However, item of mutable element can be changed
my_tuple[3][0] = 7
print(my_tuple) # (4, 2, 3, [7, 5])

# Tuples can be reassigned
my_tuple = (4, 2, 3, [6, 5])
my_tuple = (7, 2, 3, [6, 5])
print(my_tuple) # (7, 2, 3, [6, 5])

We can use + operator to combine two tuples. This is called concatenation.

We can also repeat the elements in a tuple for a given number of times using the * operator.

Both + and * operations result in a new tuple.

# Concatenating two tuples
tuple_1 = (1, 2, 3)
tuple_2 = (4, 5, 6)

print(tuple_1 + tuple_2) # (1, 2, 3, 4, 5, 6)

# Repeating a tuple
tuple_1 = ("Hello",)
print(tuple_1 * 3) # ('Hello', 'Hello', 'Hello')

Deleting a Tuple

As discussed above, we cannot change the elements in a tuple. It means that we cannot delete or remove items from a tuple.

Deleting a tuple entirely, however, is possible using the keyword del.

# Deleting tuples
my_tuple = (1, 2, 3)

del my_tuple[1] # TypeError: 'tuple' object doesn't support item deletion

del my_tuple 

print(my_tuple) # NameError: name 'my_tuple' is not defined

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Tuple Methods

Methods that add items or remove items are not available with tuple. Only the following two methods are available.

Some examples of Python tuple methods:

# Counting the number of times an item occurs in a tuple
my_tuple = ('a', 'p', 'p', 'l', 'e', 'p', 'l', 'e')

print(my_tuple.count('p')) # 3

Below is a list of Python tuple methods.

Method	Description
len()	Returns the length of the tuple
max()	Returns the largest item in the tuple
min()	Returns the smallest item in the tuple
sum()	Returns the sum of all the items in the tuple
index()	Returns the index of the first occurrence of an item in the tuple
count()	Returns the number of times an item occurs in the tuple

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Other Tuple Operations

1. Tuple Membership Test

   We can test if an item exists in a tuple or not, using the keyword in.

   # Testing if an item exists in a tuple
   my_tuple = (1, 2, 3)
   print('1' in my_tuple) # True
   print('4' in my_tuple) # False

2. Iterating Through a Tuple

   We can use a for loop to iterate through each item in a tuple.

   # Iterating through a tuple
   my_tuple = (1, 2, 3)
   for item in my_tuple:
       print(item) # 1 2 3

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Advantages of Tuple over List

Since tuples are quite similar to lists, both of them are used in similar situations. However, there are certain advantages of implementing a tuple over a list. Below listed are some of the main advantages:

• We generally use tuples for heterogeneous (different) data types and lists for homogeneous (similar) data types.

• Since tuples are immutable, iterating through a tuple is faster than with list. So there is a slight performance boost.

• Tuples that contain immutable elements can be used as a key for a dictionary. With lists, this is not possible.

• If you have data that doesn't change, implementing it as tuple will guarantee that it remains write-protected.