Tuples in Python, Lets Go!

Variables can be of the datatype tuple. A tuple is collection that cannot be modified.

It differs from a list, in that lists can be changed or modified after creation.
A tuple is defined using parenthesis ( and ) instead of [ and ] that a list uses.

If you want to change the data during program execution, use a list instead of a tuple.

Python tuple

A tuple is an immutable sequence type. A tuple is a sequence, but its values cannot be altered.

The values of a tuple cannot change. This is very important, because this is the only difference between a list.

To create a tuple, all you need to do is define a set of comma-separated values between the parenthesis.

An empty tuple would be defined as:

tup1 = ()

be careful with parenthesis, () is a tuple and [] is a list and {} a dictionary

A tuple with one item ( a comma is needed in the end ):

x = (1,) 

x = (1,2,3,4) 

You can create all kinds of tuples:

t1 = ('physics', 'chemistry', 'geography', 'history')
t2 = (1, 2, 3, 4, 5 )
t3 = ("a", "b", "c", "d")

Note: Even if your tuple has only one element, the comma is needed between the parenthesis.

Accessing tuples

To access individual elements, we use square brackets. To print the first element (Python starts counting from zero):

print(x[0]) 

print(x[1]) 

You can access tuples both in the interpreter and during code execution.
In the interpreter python, you can type commands.

Lets create a tuple

>>> t1 = ('coffee','tea','orange juice','lemonade')

Then output some elements

>>> t1[0]
'coffee'
>>> t1[1]
'tea'

And why not try to change a value

>>> t1[1] = 'water'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>>

Remember, the contents of a tuple cannot be changed after creation.

To print the last element, you can count from the back using the minus sign.

print(x[-1]) 

Tuple Unpacking

You can unpack a tuple. A package tuple object has more than one value like:

>>> t = (1,2,3)

To unpack the tuple you can do this:

>>> x,y,z = t

Then each variable (x,y,z) will contain one of the tuples values:

>>> x
1
>>> y
2
>>> z
3
>>>

When unpacking, the number of variables must match the number of values in the tuple:

>>> t = (1,2,3)
>>> x,y = t
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 2)
>>>

Tuple assignment

If you define a tuple, Python allows the parenthesis to be left out. In Python these are the same:

>>> t = (1,2,3)
>>> t = 1,2,3

So you can do unpacking like this:

>>> t = 1,2,3
>>> t
(1, 2, 3)
>>> 
>>> x,y,z = t
>>> x
1
>>> y
2
>>> z
3
>>>

So it works both if parenthesis are written or left out. For clarity, you could add them.

When in doubt, you can always call type().

>>> type(t)
<class 'tuple'>
>>>

Python tuple append

Once defined, the contents of a tuple cannot be changed.

>>> t = (1,2,3)
>>> t.append(4)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'tuple' object has no attribute 'append'
>>>

That is by design. If you want to append values, you should use a list.

Note: Tuples cannot be changed. But what you can do, is create a new tuple and overwrite it.

However, you can add a tuple to a tuple:

>>> t = t + (4,)
>>> t
(1, 2, 3, 4)
>>>

A new element has been appended at the end of the tuple, by appending two tuples.

Python tuple insert

Start with a tuple, like this:

>>> t = (1,2,4,5)

To insert a new tuple, create three tuples and the tuple to insert will go in the middle.
So you can use tuple slicing [start:end] and combine.

The example below shows how a new tuple is created with a new element in the middle:

>>> t = t[0:2] + (3,) + t[2:4]
>>> t
(1, 2, 3, 4, 5)

Python tuple modify

The contents of a tuple cannot be changed. If you try it will throw an TypeError.

>>> t[1] = 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>>

You can get around this by creating a new tuple.

>>> t = (1,2,3,4,5)
>>> t = t[0:1] + (0,) + t[2:]
>>> t
(1, 0, 3, 4, 5)
>>>

Python tuple delete

An element cannot be deleted. You can only create a new tuple without that element.

If you have this tuple:

>>> t = (1,2,3,4,5)

You can create a new one using slicing:

>>> # Create new tuple
>>> t = t[0:1] + t[2:]
>>> t
(1, 3, 4, 5)
>>>

If you want to change the contents of a tuple (append, delete, modify,…) you should use a list instead.

Python tuple to list

To convert a tuple to a list, call the list() function.

>>> # create tuple
... t = (1,2,3,4,5)

>>> # convert tuple to list
>>> mylist = list(t)

If you output mylist, you’ll see its a list:

>>> mylist
[1, 2, 3, 4, 5]
>>>

You can see the difference between lists and tuples by their parenthesis.

• Tuples use ()
• lists uses [].

Python list to tuple

A list can be converted to a tuple by calling the tuple() function:

>>> t = tuple(mylist)

Variable t is then a tuple:

>>> t
(1,2,3,4,5)

If you want to try this yourself, the exercises on PyChallenge turn the same idea into a few short problems with instant feedback.