How can I iterate over only the first variable of a tuple

Question

In python, when you have a list of tuples, you can iterate over them. For example when you have 3d points then:

for x,y,z in points:
    pass
    # do something with x y or z

What if you only want to use the first variable, or the first and the third. Is there any skipping symbol in python?

Answer 1

Is something preventing you from not touching variables that you're not interested in? There is a conventional use of underscore in Python to indicate variable that you're not interested. E.g.:

for x, _,_ in points:
    print(x)

You need to understand that this is just a convention and has no bearing on performance.

Answer 2

Yes, the underscore:

>>> a=(1,2,3,4)
>>> b,_,_,c = a
>>> b,c
(1, 4)

This is not exactly 'skipping', just a convention. Underscore variable still gets the value assigned:

>>> _
3