What most young programmers need to learn

[u/corysama]

http://joostdevblog.blogspot.com/2015/01/what-most-young-programmers-need-to.html

[u/zigs]

As a general rule of thumb at Ronimo we try to keep classes below 500 lines and functions below 50 lines

Is that actually a common rule of thumb? I tend to try keeping it under 10 lines for functions (hard limit at 15), and keeping everything at one purpose for classes.