[Python-ideas] Where-statement (Proposal for function expressions)

[Gerald Britton]

Sometimes I use helper functions to make things easier to read.
However, I don't like unnecessary function calls since they are
expensive in Python compared to other languages. Still I might do
this:

def foo(x):
  def bar(y):
      ...
      return ... #something depending on y
  ...
  return bar(z)

If I had a "where" clause I could write:

def foo(x):
   ...
   return y where:
        #compute y


Using "where" would have the advantage of avoiding a function call,
though I suppose it wouldn't save (much) stack space since it needs a
new scope anyway.  I see the "where" clause as a useful way to
abstract a section of code to keep the high level in view, then break
it down as you go.