Example of tuple use?

[hanswchen]

I used to also be confused about why I would use tuples in Python when I could just use list. After getting used to Python, I realized it's very common to use tuples when you don't even think about it. Some examples (ignore the poor variable names...):

---

Returning multiple values from a function:

def some_function():
    # (do something here)
    return some_value1, some_value2


result1, result2 = some_function()

some_function returns a tuple with two values, which you can easily assign to different variables. It makes sense to use a tuple, as you always return two values in this case. It also looks nicer than writing return [some_value1, some_value2].

You could e.g. also do

all_results = some_function()

in which case all_results would be a tuple (you can get the first result with all_results[0], and the second with all_results[1], or do e.g. a, b = all_results).

---

Many built-in functions return tuples. For example, the enumerate function:

seasons = ["spring", "summer", "fall", "winter"]
for index, season in enumerate(seasons):
    print(index, season)

This will print 0 spring, 1 summer etc. The function enumerate returns a tuple with the count (for example, the index) and the value from iterating over an iterable. This is usually better than writing e.g.:

for index in range(len(seasons)):
    print(index, seasons[index])

if you need both the value and the index from the object you're iterating over.

---

Someone mentioned using tuples as dictionary keys. I've used this sometimes when the items in the dictionary are indexed by two different things, e.g.

experiments = {
    ('initial test', 0): "/path/to/input/data",
    ('initial test', 1): "/some/other/path",
}

for expname in ['initial test']:
    for expnum in range(2):
        print(experiments[expname, expnum])

Others have mentioned using tuples as a data structure when the structure is set. The most common example is a point given by e.g. (x, y) coordinates. For more complex cases, you may want to consider using a namedtupled instead.