11.7 Built-in Functions and Traversal

Built-in Functions

The same general-purpose sequence functions that work on lists (see 10.8 Built-in Functions) work identically on tuples.

>>> len((3, 1, 4, 1, 5))
5
>>> max((3, 1, 4, 1, 5)), min((3, 1, 4, 1, 5))
(5, 1)
>>> sum((3, 1, 4, 1, 5))
14
>>> any((0, 0, 1)), all((1, 1, 1))
(True, True)

sorted()

Always returns a list, even when given a tuple as input — there’s no in-place tuple.sort(), since tuples can’t be modified.

>>> sorted((3, 1, 4, 1, 5))
[1, 1, 3, 4, 5]

Traversing Tuples

for Loop

>>> for x in (1, 2, 3):
...     print(x, end=" ")
1 2 3

while Loop

i = 0
t = (10, 20, 30)
while i < len(t):
    print(t[i], end=" ")
    i += 1
# Output: 10 20 30

enumerate()

>>> for i, v in enumerate(("a", "b", "c")):
...     print(i, v)
0 a
1 b
2 c

Quick Interview Answer

“Every general-purpose sequence function — len, max, min, sum, any, all — works identically on a tuple as it does on a list, since they only rely on the iterable and comparison protocols, not mutability. The one worth calling out specifically is sorted(): it always returns a list, regardless of what type went in, because there’s no such thing as an in-place tuple.sort() — sorting a tuple’s elements necessarily means producing a different object. Traversal is identical to lists too: for is the default, while for manual index control, enumerate() for index-value pairs without a counter.”

Common Mistakes

• Expecting sorted(some_tuple) to return a tuple back — it always returns a list; wrap in tuple(sorted(...)) if a tuple result is actually needed.
• Calling some_tuple.sort() expecting in-place sorting like a list — tuples have no sort() method at all (see 11.6 Tuple Methods).
• Using a while loop with manual indexing when a plain for loop accomplishes the same traversal more simply.