We have a new #1 at T40 this week, as Shawn Mendes' "There's Nothing Holdin' Me Back" (Island/Republic) moves up to claim the spot. Charlie Puth's "Attention" will leap into the Top 3 and in contention for being the Greatest Gainer, while DJ Khaled's "Wild Thoughts" f/Rihanna & Bryson Tiller (We The Best/Epic) makes the jump to Top 5. Calvin Harris' "Feels" f/Pharrell, Katy Perry and Big Sean (Columbia) goes Top 10. Post Malone's "Congratulations" f/Quavo (Republic) joins the Top 20 and Louis Tomlinson's "Back To You" f/Bebe Rexha (Syco/Epic) joins the Top 30.  Charting this week is Caroline's Hey Violet with "Hoodie," and watch for RCA's newly-dropped single from P!NK called "What About Us" to possibly leap into the Top 30 on less than a week of airplay.