Python Tuples

A tuple is like a list, but once created, you can’t edit it. A tuple is immutable. You create a tuple by adding items between parentheses ().

Here is an example where we create two tuples:

>>> hostnames = ("H1","SW1","R1","ASA1")
>>> my_numbers = (1,2,3,4,5)

We can access items in the tuple by specifying the index number in brackets [] behind the tuple:

>>> hostnames = ("H1","SW1","R1","ASA1")
>>> my_numbers = (1,2,3,4,5)

Will show this output:

>>> print(hostnames[2])
R1

>>> print(my_numbers[3])
4

Adding or removing items in a tuple

A tuple is immutable so you can’t modify it like a list. For example, try adding something to the tuple:

>>> hostnames = ("H1","SW1","R1","ASA1")
>>> hostnames.append("SW2")

Will show this output:

Traceback (most recent call last):
  File "", line 1, in 
    hostnames.append("SW2")
    ^^^^^^^^^^^^^^^^
AttributeError: 'tuple' object has no attribute 'append'

It’s a tuple, not a list, so the append attribute doesn’t exist.  You also can’t delete anything from the tuple:

>>> hostnames = ("H1","SW1","R1","ASA1")
>>> hostnames.pop(2)

Will show this output:

Traceback (most recent call last):
  File "", line 1, in 
    hostnames.pop(2)
    ^^^^^^^^^^^^^
AttributeError: 'tuple' object has no attribute 'pop'

The tuple doesn’t have a pop attribute to remove items.

You could use a tuple to “write protect” the contents of the tuple since you can’t modify it. However, it is possible to re-declare a tuple. Here is an example:

>>> hostnames = ("H1","SW1","R1","ASA1")
>>> hostnames = ("H3","SW4","R8")

>>> print(hostnames)

Will show this output:

('H3', 'SW4', 'R8')

Above, I re-declared the variable “hostnames” with a new tuple. This is no problem in Python so the “write protect” analogy doesn’t make much sense.

Tuple vs List

Why would you want to use a tuple instead of a list?

To be honest, for us network engineers it doesn’t matter much.