In the 1975 software project management book, The Mythical Man Month: Essays on Software Engineering, Fred Brooks states that, no matter the programming language chosen, a professional developer will write an average 10 lines of code (LoC) per day.

Productivities in [the] range of 600-800 debugged instructions per man-year were experienced by control program groups. Productivities in the [range of] 2000-3000 debugged instructions per man-year were achieved by [OS/360] language translator groups. These include planning done by the group, coding component test, system test, and some support activities.

-Page 93 of "The Mythical Man Month" (1975)

https://skeptics.stackexchange.com/questions/17224/do-professional-software-developers-write-an-average-of-10-lines-of-code-per-day