Update tuples in Python (Add, change, remove items in tuples)

Posted: 2020-07-22 / Tags: Python

Since tuples tuple in Python are immutable sequences, you can not update them. You can not add, change, remove items (elements) in tuples.

tuple represent data that you don't need to update, so you should use list rather than tuple if you need to update it. However, if you really need to update tuple, you can convert it to list, update it, and then turn it back into tuple.

Here, the following contents will be described.

  • Tuples are immutable
  • Concatenate multiple tuples
  • Add / insert items to tuples
  • Change items in tuples
  • Remove items in tuples

Note that, although words such as "add", "change", "remove" are used for convenience, but in reality, a new object is generated, and the original object is not updated.

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Tuples are immutable

Take the following tuple as an example.

t = (0, 1, 2)

# (0, 1, 2)

# <class 'tuple'>

You can get elements by index [] or slice [:] like lists.

# 0

# (0, 1)

Tuples are immutable, so you can not assign a new value to an element.

# t[0] = 100
# TypeError: 'tuple' object does not support item assignment

Destructive methods (= methods that update the original object) such as append() in list are not defined in tuple.

# t.append(100)
# AttributeError: 'tuple' object has no attribute 'append'

Concatenate multiple tuples

Tuples are immutable, but you can concatenate multiple tuples with the + operator. At this time, the original object remains unchanged and a new object is generated.

t_add = t + (3, 4, 5)

# (0, 1, 2, 3, 4, 5)

# (0, 1, 2)

Only tuples can be concatenated. It cannot be concatenated with other types such as lists.

# print(t + [3, 4, 5])
# TypeError: can only concatenate tuple (not "list") to tuple

If you want to add only one element, you can concatenate a tuple with one element.

t_add_one = t + (3,)

# (0, 1, 2, 3)

Note that a tuple with one element requires a comma at the end.

Add / insert items to tuples

If you want to add new items at the beginning or the end, you can concatenate it with the + operator as described above, but if you want to insert new items at any position, you need to convert a tuple to a list.

Convert tuple into list with list().

l = list(t)

# [0, 1, 2]

# <class 'list'>

Insert an item with insert().

l.insert(2, 100)

# [0, 1, 100, 2]

Convert list into tuple with tuple().

t_insert = tuple(l)

# (0, 1, 100, 2)

# <class 'tuple'>
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Change items in tuples

The flow is the same when changing items. Convert tuple to list, update it, and turn it back into tuple.

l = list(t)
l[1] = 100
t_change = tuple(l)

# (0, 100, 2)

Remove items in tuples

The same flow can be used to remove items.

l = list(t)
t_remove = tuple(l)

# (0, 2)

In the above example, remove() is used, but it is also possible to use pop() and del.

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