is there any principle when writing python function

[Roy Smith]

In article <j305uo$pmd$1 at solani.org>, Peter Otten <__peter__ at web.de> 
wrote:

> smith jack wrote:
> 
> > i have heard that function invocation in python is expensive, but make
> > lots of functions are a good design habit in many other languages, so
> > is there any principle when writing python function?
> > for example, how many lines should form a function?
> 
> Five ;)

Five is right out.