Python: tuples

A tuple is just like a list, consist of number of values separated by commas.

Differences between tuple and list

a.   List is mutable, where as tuple is immutable

b.   Tuple can contain heterogeneous data, where as list usually contains homogeneous data.

test.py

employee=(1, "Hari Krihsna", "Gurram", 12345.678)

print(employee)
print(employee[0])
print(employee[1])
print(employee[2])
print(employee[3])

$ python3 test.py

(1, 'Hari Krihsna', 'Gurram', 12345.678)

1

Hari Krihsna

Gurram

12345.678

As you observe above example, elements in tuple are enclosed in parenthesis. Eventhough tuples are immutable, you can create tuples which contain mutable objects, such as lists.

test.py

employee=(1, [])

print(employee)

employee[1].append(2)
employee[1].append(4)
employee[1].append(6)

print(employee)

$ python3 test.py

(1, [])

(1, [2, 4, 6])

Packing and unpacking

You can define tuples, without using parenthesis.

For example,

employee=1, "Hari Krihsna", "Gurram", 12345.678

Above one is the example of tuple packing.

id, firstName, lastName, salary = employee

Above one is an example of tuple unpacking. Sequence unpacking requires that there are as many variables on the left side of the equals sign as there are elements in the sequence.

test.py

employee=1, "Hari Krihsna", "Gurram", 12345.678

id, firstName, lastName, salary = employee

print(id)
print(firstName)
print(lastName)
print(salary)

$ python3 test.py

1

Hari Krihsna

Gurram

12345.678

Concatenate tuples

‘+’ operator is used to concatenate tuples.

>>> tuple1=(1, "HI", 2, 45.65)
>>> tuple2=("abcdef", 54, 67)
>>> tuple3=tuple1+tuple2
>>> tuple3
(1, 'HI', 2, 45.65, 'abcdef', 54, 67)

Slicing

Just like lists, you can access tuples using slice notation.

Example	Description
tuple[start:end]	Returns tuple from index start (included) to end index (excluded).
tuple[:end]	Returns tuple from index 0(included) to end index (excluded).
tuple[start:]	Return tuple from index start to till end.
tuple[-2:]	Return elements from 2nd last to end.

>>> tuple1
(1, 'HI', 2, 45.65)
>>> tuple1[0:]
(1, 'HI', 2, 45.65)
>>> tuple1[:]
(1, 'HI', 2, 45.65)
>>> tuple1[:3]
(1, 'HI', 2)
>>> tuple1[2:5]
(2, 45.65)

‘*’: Repeat tuple elements

‘*’  is the repetition operator, used to repeat the elements of tuple.

>>> tuple1
(1, 'HI', 2, 45.65)
>>> 
>>> tuple1*3
(1, 'HI', 2, 45.65, 1, 'HI', 2, 45.65, 1, 'HI', 2, 45.65)
>>> 

Remove tuple elements

As I said, tuples are immutable, so it is not possible to remove elements from tuple. But you can remove the entire tuple using del statement.

>>> tuple1=(1, "HI", 2, 45.65)
>>> 
>>> del tuple1
>>> tuple1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'tuple1' is not defined

Observe the output, an exception raised; this is because after deletion, tuple does not exist any more.

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