[Tutor] Difference between filter and map

[vanam]

ya i am sure about that i am using python editor which has python
intrepreter attached to it i got the same output for both filter and map
def squ(n):
   y = n*n
  print y
filter(y,range(3))->0  1 4
map(y,range(3))->0 1 4

On 1/23/07, Kent Johnson <kent37 at tds.net> wrote:
>
> vanam wrote:
> > i want to know the difference between filter(function,sequence) and
> > map(function,sequence).I tried for a simple script with an function
> > which finds the square of the number,after including separately filter
> > and map in the script i am getting the same results for instance
> > def squ(x):
> >      return x*x
> > filter(squ,range(1,3))->1,4(output)
> > map(squ,range(1,3)->1,4(output)
>
> Are you sure about that? I get
>
> In [1]: def sq(x): return x*x
>     ...:
>
> In [2]: filter(sq, range(3))
> Out[2]: [1, 2]
>
> In [3]: map(sq, range(3))
> Out[3]: [0, 1, 4]
>
> map(fn, lst) returns a new list with fn applied to each element of lst.
> In terms of list comprehensions, it is [ fn(x) for x in lst ].
>
> filter(fn, lst) returns a new list containing all elements of the
> original list for which fn(x) is true. As a list comprehension, it is
> [ x for x in lst if fn(x) ]
>
> Kent
>
>


-- 

                                           Vanam
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