Group Related Values Into Tuples

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Problem to Solve

I want to collect a few values together into a group that I can treat as one "thing", and that won’t need to change.

In python, a tuple is an ordered collection of items. Unlike a list a tuple cannot be modified after it has been created: we say that tuples are immutable.

Rather than reinvent the wheel, I'll direct you to some on line introductions to tuples:

• W3 Schools: Python Tuples

• Geeks for Geeks: Tuples in Python

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A Few Recipes

In all of these, we'll use the variable names t, t1, t2, etc. to refer to tuples.

create a tuple explicitly

t1 = (1, 2, 3, 4, 5)  # a tuple of 5 integers (a "five-tuple")
t2 = 1, 2, 3, 4, 5  # parentheses can be omitted IF the result is unambiguous
t3 = ('electron', 'muon', 'tau')  # a three-tuple of strings
t4 = ((1, 2), (11, 12), (21, 22))  # a 3-tuple of 2-tuples
t5 = (22/7, math.pi, math.sqrt(2))  # elements can be the result of expressions

create a tuple from a different collection type

list1 = [1, 2, 3, 4, 5]  # a list of integers
t1 = tuple(list1)  # from a list
t2 = tuple('abc')  # from a string: yields ('a', 'b', 'c')
t3 = tuple(range(5))  # from a range object: yields (0, 1, 2, 3, 4)

create an empty or one-element tuple

t1 = ()  # an empty tuple
t2 = tuple()  # another empty tuple
t3 = (3-2j,)  # a one-element tuple (note the comma)
t4 = tuple([22/7])  # another one-element tuple

determine the length of a tuple

t1 = (3, -2, 14, 7, 0)  # a 5-tuple
len(t1)  # yields 5

access individual elements of a tuple

t1 = (3, -2, 14, 7, 0)  # a 5-tuple
t1[0]  # yields 3
t1[1]  # yields -2
t1[-1]  # yields 0 (the last element)
t1[-2]  # yields 7 (the second-to-last element)

change the value of a tuple — NOPE!

t1 = (5, 12, 13)  # a 3-tuple
t1[1] = -12  # TypeError: tuples are immutable!
t1 = (t1[0], -12, t1[2])  # must create a new tuple with the new value(s)

concatenate two tuples

t1 = (1, 2, 3)  # a 3-tuple
t2 = (4, 5, 6)  # another 3-tuple
t3 = t1 + t2  # yields (1, 2, 3, 4, 5, 6)

create a repeating tuple

If you, for some reason, want to create a tuple with the same value repeated multiple times, you can do it like this:

t1 = (1, 2, 3)  # a 3-tuple
t2 = t1 * 3  # yields (1, 2, 3, 1, 2, 3, 1, 2, 3)

The original tuple that gets repeated could have only one element, or two, or 17 as you wish.

nest tuples

t1 = (1, 2, 3)  # a 3-tuple
t2 = (4, 5, 6)  # another 3-tuple
t3 = (t1, t2)  # a 2-tuple of 3-tuples
t4 = ((1, 2), (11, 12), (21, 22))  # a 3-tuple of 2-tuples

access elements of a tuple one at a time

for one_value in t1:
    print(one_value)  # or do anything else with the value