Taking into account Psalm 147:2, this Psalm can be dated after the exile.
This psalm contains many quotations from other Bible passages. The author uses these Bible passages and his own words to create a song of praise. The Lord is praised for his care and attention to creation, for his servants, for the oppressed, and for the land and people of Israel, including a special place for Jerusalem.
It is very clear that this Psalm is a song of praise. Three times there is a call to praise the Lord: in Psalm 147:1, Psalm 147:7, and Psalm 147:12.
1 Praise the LORD! For it is good to sing praises to our God; for it is pleasant, and a song of praise is fitting.