# [Tutor] Lambda

**Glen Wheeler
**
wheelege@hotmail.com

*Tue, 5 Feb 2002 17:12:27 +1100*

Hi Greg,
Sure thing. I myself really like lambdas...here is not one line, but I
hope it helps shed some light -
>>>* def multiply(a,b):
*... return a*b
...
>>>* for i in range(5):
*... print multiply(i,2)
...
0
2
4
6
8
That should be easy to understand, although you may think it a little
weird that I wrote multiply(i,2) instead of i*2. But what this does is
applies the function multiply (with the second parameter as 2) over the
sequence range(5) - obviously doubling every number in the sequence. Here
is the same thing but with a lambda -
>>>* for i in range(5):
*... print (lambda x,y:x*y)(i,2)
...
0
2
4
6
8
The whole function object is contained in (lambda x,y:x*y). This is
horribly inefficient, but still it's a learning exercise. Here is something
similar using a very cool function called map -
>>>* map(lambda x:x*2, range(5))
*[0, 2, 4, 6, 8]
Try typing that into the interactive interpreter. What that line says is
'apply the function 'lambda x:x*2' to the sequence 'range(5)'. All that
means is double each element. Donb't worry if you don't get the map - that
was just a little extra bit :)
Good luck!
Glen
----- Original Message -----
From: "Greg Guest" <greg.guest@3web.net>
To: <tutor@python.org>
Sent: Tuesday, February 05, 2002 1:28 PM
Subject: [Tutor] Lambda
Hi everyone,
Emboldened by Jeff Shannon's remark of a couple of weeks ago that he finds
lambdas counterintuitive, I ask my first question to the tutor.
I not only find them counterintuitive, but can't even figure out what they
do in a line of code. I would be grateful if someone could translate a line
using lambda into one that doesn't.
I've been reading the tutor for a couple of months now, and find it a
wonderful place. The threads on Classes have helped me a lot.
TIA
Greg Guest
A Palindrome:
Straw? No, too stupid a fad. I put soot on warts.
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