Is a post required in a front tooth? Has a crack up the side and has been root canaled.

Hard to say if it is necessary without exam and xray, and even amongst dentists there is much debate about them.  It is your tooth and your decision, so if you don't want one you can ask for the space to be filled with a core material and a crown placed.  It may still fracture, but at least you are aware of the risks and chose to take them.

If there is adequate tooth structure remaining, then the dentist can fill in the post prep with a bonded core material and go ahead with the crown WITHOUT doing a post.