Difference between revisions of "Python-3.4.3/C3/Getting-started-with-tuples/English"

Learning Objectives

1. Understand what tuples are
2. Compare tuples with lists
3. Know why they are needed and
4. Learn to use them.

System Specifications

• Ubuntu Linux 16.04 operating system
• Python 3.4.3 and
• IPython 5.1.0

Pre-requisites

• run basic Python commands on the ipython console
• use lists

If not, see the relevant Python tutorials on this website.

Tuples in Python

• Tuple is a collection of elements similar to a list.
• Tuple uses parentheses, whereas list uses square brackets.
• Elements of a tuple cannot be changed once it is assigned.
• But in a list, elements can be changed.

Tuple declaration

(1, 2.5) and 1, 2.5 are same

(1, ) and 1, are same

((1,),) and (1,), are same

Inside brackets 1, 2.5 is a tuple with two elements.

The same can be declared as 1, 2.5.

Inside brackets 1 comma is a tuple with one element.

The same can be declared as 1 comma

Inside brackets again inside brackets 1 comma and outside bracket a comma is a tuple with one tuple as element.

The same can be declared as inside brackets 1 comma and outside bracket a comma.

Open the terminal.

From here onwards, remember to press the Enter key after typing every command on the terminal.

Type, t is equal to inside brackets 1 comma 2.5 comma inside double quotes hello comma -4 comma inside double quotes world comma 1.24 comma 5

Highlight , and parentheses

It is similar to list except that parentheses are used instead of square brackets.

At least one comma is mandatory for a tuple.

The brackets are optional, but should be added for clarity.

Type, t inside square brackets 3

It prints the corresponding slice.

Type, t inside square brackets 2 is equal to inside double quotes Hello

We can see that, it raises an error saying 'tuple object does not support item assignment'.

It shows, elements of a tuple cannot be changed after it is created.

This is called immutability.

print(x)

Type,

for x in t colon

print inside brackets x

It prints each element of the tuple t.

<<PAUSE>>

Try this exercise and then resume the video.

Exercise 1

Given, a is equal to 5 and b is equal to 7, swap the values of a and b.

a = 5

b = 7

a

b

a is equal to 5

b is equal to 7

Then type, a

Type, b

temp = a

a = b

b = temp

a

b

Highlight the outputs

Type

temp is equal to a

a is equal to b

b is equal to temp

Then type, a

Type, b

We can see that the values are successfully swapped now.

But this is the traditional approach.

a = 5

b = 7

a, b = b, a

a

b

Type

a is equal to 5

b is equal to 7

a, b is equal to b, a

Now we will check whether the values are swapped.

Type, a

Type, b

We can see that the values are swapped easily.

a = 2.5

b = "hello"

a, b = b, a

a

b

Type,

a is equal to 2.5

b is equal to inside double quotes hello

a, b is equal to b, a

Now to check the values, type, a

Type, b

<<PAUSE>>

This is called tuple packing and unpacking.

When you type, a comma b is equal to b comma a

First the values of b and a are packed into a tuple on the right side. Then it is unpacked into the variables a and b.

Highlight the output

Type, 5 comma

We can see a tuple with one element.

Now it is a tuple with three elements.

When we type two or more elements separated by commas, those elements are packed into a tuple.

Immutability of tuples ensures that the values are not changed during the packing and unpacking.

Summary slide

In this tutorial, we have learnt about,

• Tuples
• Similarities of tuples with lists
• Immutability of tuples and
• Concept of Packing and unpacking of tuples.

Evaluation

1. Define a tuple containing two values as given below. The first value is integer 4 and the second value is float 2.5.
2. If we type, a is equal to 5 comma then what is the datatype of a?
3. If we type, a is equal to inside brackets 2 comma 3 a inside square brackets 0 comma a inside square brackets 1 is equal to inside brackets 3 comma 4 What is the output?

Solutions

1. A tuple is defined by enclosing parentheses around a sequence of items separated by commas. Hence, we write our tuple as, inside brackets 4 comma 2.5
2. Since the given data is 5 followed by a comma, it is a tuple
3. The given operation will give a TypeError because tuples are immutable.

For more details, visit this website.

Thanks for watching.