Python Tuples

Tuple

A tuple stores several items in one variable.

It is one of the 4 built-in types Python offers for collections of data. The others are List, Set and Dictionary, and each has its own qualities and uses.

What sets a tuple apart is that it is ordered and unchangeable.

You write one using round brackets.

Example

Building a simple tuple:

Create a tuple with three fruit names and print it.
> Output: complete Python program

Prompt

Create a tuple with three fruit names and print it.

Output: complete Python program

Intro

mytuple = ("apple", "banana", "cherry")

Tuple Items

Three things define tuple items: they keep their order, they cannot be changed, and the same value may appear more than once.

Each item also has an index. Counting starts at zero, so index [0] is the first item, index [1] is the next one, and so on.

Ordered

Being ordered means a tuple keeps its items in a set sequence, and that sequence stays put.

Unchangeable

A tuple is fixed once it exists: you can't change its items, add new ones or remove any.

Allow Duplicates

Because every item has its own index, two items can share a value without any conflict:

Example

Here "apple" and "cherry" each appear twice:

Create a tuple that contains duplicate values and print it.
> Output: complete Python program

Prompt

Create a tuple that contains duplicate values and print it.

Output: complete Python program

thistuple = ("apple", "banana", "cherry", "apple", "cherry")
print(thistuple)

Tuple Length

The len() function tells you how many items a tuple holds:

Example

Count the items and print the result:

Create a tuple with three items and print the number of items using len().
> Output: complete Python program

Prompt

Create a tuple with three items and print the number of items using len().

Output: complete Python program

Create Tuple With One Item

A tuple with a single item needs a comma after that item. Without the comma, Python won't treat it as a tuple.

Example

The comma makes all the difference:

Create a one-item tuple with a trailing comma and print its type. Then create one without the comma and print its type to show the difference.
> Output: complete Python program

Prompt

Create a one-item tuple with a trailing comma and print its type. Then create one without the comma and print its type to show the difference.

Output: complete Python program

thistuple = ("apple",)
print(type(thistuple))

#NOT a tuple
thistuple = ("apple")
print(type(thistuple))

Tuple Items - Data Types

A tuple can hold values of any data type:

Example

One tuple each of strings, integers and booleans:

Create three tuples: one with strings, one with integers, and one with boolean values.
> Output: complete Python program

Prompt

Create three tuples: one with strings, one with integers, and one with boolean values.

Output: complete Python program

tuple1 = ("apple", "banana", "cherry")
tuple2 = (1, 5, 7, 9, 3)
tuple3 = (True, False, False)

Example

A single tuple can also mix those types:

Create a tuple containing a mix of strings, integers, and boolean values.
> Output: complete Python program

Prompt

Create a tuple containing a mix of strings, integers, and boolean values.

Output: complete Python program

type()

To Python, a tuple is an object whose data type is 'tuple':

Example

Ask Python for the type of a tuple:

Create a tuple and print its data type using the type() function.
> Output: complete Python program

Prompt

Create a tuple and print its data type using the type() function.

Output: complete Python program

The tuple() Constructor

You can also build a tuple by calling the tuple() constructor.

Example

Making a tuple with the tuple() constructor:

Use the tuple() constructor to create a tuple and print it.
> Output: complete Python program

Prompt

Use the tuple() constructor to create a tuple and print it.

Output: complete Python program

Python Collections (Arrays)

Python gives you four collection data types, and each one behaves a little differently:

List keeps its order and can be changed. Duplicates are fine.
Tuple keeps its order but cannot be changed. Duplicates are fine.
Set has no order and no indexes, and is unchangeable*. Duplicates are not allowed.
Dictionary keeps its order** and can be changed. Duplicates are not allowed.

*You can't change the items of a set once they are in it, but you are free to add new ones or take existing ones out at any time.

**Dictionaries are ordered from Python 3.7 onward. In Python 3.6 and earlier they are unordered.

It pays to know these properties before you pick a type for your data. The right choice can keep the meaning of the data intact, and it can also make your program more efficient or more secure.