Extracting the a value from a tuple when the other values are unused

Question

I have a tuple foo which contains something I don\'t care about and something I do.

foo = (something_i_dont_need, something_i_need)

<

Answer 1

Both are acceptable, and I've seen both in production code. I think the choice upon the context, the intent, and the local style.

There is also a third option where the code describes the unused value:

_real, imaginary = foo

I use all three within my code depending upon which is clearest:

_, x = foo

• When the tuple is small.
• When there are few discarded values.
• When there are few discarded values relative to the number of extracted values.
• The reader probably knows the tuple's composition, and the composition of the whole tuple is important.
• When it's customary to think about the structure of the tuple as a single unit

x=foo[i]

• When the tuple is large.
• When there are many discarded values for some value of many.
• When the reader probably knows the tuple's composition.
• The rest of the tuple's values are completely and utterly irrelevant & offer no useful information for the reader.
• When it's customary to think about the structure as a sequence.
• When the tuple has uniform composition.
• When it's customary to use an index for the datatype.
• When the index is keyed in a loop.
• When the reader's attention should be drawn to the index's value.

_real, imaginary = foo

• When the tuple is small.
• When there are few discarded values.
• When the reader probably doesn't know the tuple's composition.
• When naming the discarded value gives the reader insight. (You can guess from this one line that foo is a complex number.)