lambda

[Terry Reedy]

<rubbishemail at web.de> wrote in message 
news:1145642409.389741.39680 at g10g2000cwb.googlegroups.com...
> Hello,
>
> I need your help understanding lambda (and doing it a better way
> without).
>
> f  = lambda x : x*x

There is no reason to ever write name=lambda...

def f(x): return x*x

is better because it attaches the name to the function for tracebacks.

> # this is a list of functions
> [f for y in range(1,5)]
>
> [f for y in range(1,5)][0](2)
> # returns 4, as expected
>
>
> # ok now I want a list like
> # [x^2, 2*x^2, 3*x^2,...]

Given:

def makef(multiplier):
   def f(x): return multiplier*x*x
   return f

> [f*y for y in range(5)]

I believe

[makef(y) for y in range(5)]

will do what you want.

The slightly abbreviated lambda form is never necessary, that I know of, 
and notoriously confusing when used in list comprehensions.  So I advise 
don't.

Terry Jan Reedy