What was the Attendance during the Home game where St. Johnstone was the Opponent?
CREATE TABLE "scottish_premier_league" (
  "date" text,
  "opponent" text,
  "venue" text,
  "result_celtic_score_first" text,
  "attendance" real,
  "match_report" text
);
SELECT COUNT("attendance") FROM "scottish_premier_league" WHERE "opponent"='st. johnstone' AND "venue"='home';