Need to calculate values for multiple records with a commond ID # ArcPY

I have a table "Projects" with multiple project ID's and multiple records per project ID. I want to take the sum of values in multiple fields and combine them based on project ID. For example Project A might have 3 records with varying data between records for a field called "Labor_Hours". I want to get the sum of Labor_Hours for all records with a project ID or "Project A" by using Arcpy. I could use the field calculator to only calulate values for Project A, however I will have varying project IDs when importing new records every week.

In summary, i want my Arcpy script to run calculations for a set of records with the same Project ID Any suggestions?