breast pump

Rhiannon • \\Mama to Oscar & Amelia 💙 Wife to Gerard//
I know this will probably sound like a silly question. 
But I plan to exclusively breast feed if all goes to plan. 
I'm wondering whether buying a breast pump is necessary? 
Obviously it would definatly come in handy to store milk. 
But are there any other benifits of using one? 
I'm asking because I want to know if I should purchase one before the baby is born or if I could get away with buying one after?