Note that the word, periodista, relates to the English word, periodical, which is a monthly (or whatever) magazine which is published in established and expected periods. A writer of such publications could be called, in Engish, a "periodicalist" like it is in Spanish, but is called a journalist, instead, which roughly means the same thing as periodista, though the period specifide in the word, "journalist," is daily.
It ends with -ista. Words that end like this can always be masculine or feminine
it doesn't always depend on what the word ends with, sometimes it depends on the word in the begining, in this case ''el'', is the first word, so it is masculine, the same is true with ''la'', witch would be femenine
Most of the time, if something ends in -ista, its masculine; such as deportista.
if you love unicorns so much, guess what?! a man found a skull of a deer in a forest but the horns were slightly deformed so there was only one horn on the top of its head that looked exactly like a unicorn skull!