Re: Filter function and lists

[Terry Reedy]

John Townsend wrote:

I’m trying to figure out how to use filter to walk through a list.
>
If I try a simple scripts like this:
>
def greaterthanten (number):
#pdb.set_trace( )
if (number 10):
ret_val = 1
>
else:
ret_val = 0
>
return ret_val
>
old_list = [1,2,20,30,5]
>
new_list = filter(greatert hanten, old_list)
>
#new_list becomes [20, 30]
>
The script works as I would expect. However, what if I need to pass more
than one argument to the function? Can I do that with filter? Or does
filter work only with function that take only a single arg?

The latter. Other functions could be wrapped to bind all parameters
except the list element. Or write an explicit loop.

[Mensanator]

Re: Filter function and lists

On Oct 29, 4:28 pm, Terry Reedy <tjre...@udel.e duwrote:

John Townsend wrote:

I’m trying to figure out how to use filter to walk through a list.

>

If I try a simple scripts like this:

>

def greaterthanten (number):
                #pdb.set_trace( )
                if (number 10):
                                ret_val= 1

>

                else:
                                ret_val= 0

>

                return ret_val

>

old_list = [1,2,20,30,5]

>

new_list = filter(greatert hanten, old_list)

>

#new_list becomes [20, 30]

>

The script works as I would expect. However, what if I need to pass more
than one argument to the function? Can I do that with filter? Or does
filter work only with function that take only a single arg?

That single argument could be a list.

>>old_list = [1,2,20,30,5]

>>def power_of_10(a):

if a[0]%10==0 and a[0]<a[1]:
return True
else:
return False

>>new_list = [i[0] for i in filter(power_of _10,[[i,the_limit] for i in old_list])]
>>new_list

[20, 30]

>>the_limit = 25
>>new_list = [i[0] for i in filter(power_of _10,[[i,the_limit] for i in old_list])]
>>new_list

[20]

>
The latter.  Other functions could be wrapped to bind all parameters
except the list element.  Or write an explicit loop.- Hide quoted text -
>
- Show quoted text -