Python: Creating a filter function

Question

I'm trying to create a function:

filter(delete,lst)

When someone inputs:

filter(1,[1,2,1])

returns [2]

What I have come up with was to use the list.remove function but it only deletes the first instance of delete.

def filter(delete, lst):

"""

Removes the value or string of delete from the list lst

"""

   list(lst)

   lst.remove(delete)

   print lst

My result:

filter(1,[1,2,1])

returns [2,1]

http://stackoverflow.com/questions/1157106/remove-all-occurences-of-a-value-from-a-python-list — Chad, Nov 18 '11 at 02:00
I'd suggest choosing a different name for your function. There is a built-in `filter` function and you'll be masking it. — Avaris, Nov 18 '11 at 02:00
the reason i called my function "filter" was at the request of the instructor in this assignment — HighAllegiant, Nov 18 '11 at 02:06
Does this answer your question? [Remove all occurrences of a value from a list?](https://stackoverflow.com/questions/1157106/remove-all-occurrences-of-a-value-from-a-list) — Georgy, Feb 19 '20 at 15:21

score 8 · Accepted Answer · answered Nov 18 '11 at 01:58

8

Try with list comprehensions:

def filt(delete, lst):
    return [x for x in lst if x != delete]

Or alternatively, with the built-in filter function:

def filt(delete, lst):
    return filter(lambda x: x != delete, lst)

And it's better not to use the name filter for your function, since that's the same name as the built-in function used above

answered Nov 18 '11 at 01:58

Óscar López

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+1. I'd only add that it's good not to use `filter` as a name, since it's already a built-in. – Michael Hoffman Nov 18 '11 at 02:01
Thanks for the answers. And the reason I called my function "filter" was at the request of my instructor in this assignment. – HighAllegiant Nov 18 '11 at 02:08
2

HighAllegiant : In those cases, **please** add the Homework tag to your question. Giving the answer to you in absolutely unhelpful. – Vincent Savard Nov 18 '11 at 02:38
Between this and your other question, it looks to me like your instructor is hell-bent on making people do easy problems the hard way for no reason. :( – Karl Knechtel Nov 18 '11 at 03:51

score 0 · Answer 2 · edited Jun 20 '20 at 09:12

0

Custom Filter Function

def my_filter(func,sequence):
    res=[]
    for variable in sequence :
        if func(variable):
            res.append(variable)
    return res

def is_even(item):
    if item%2==0 :
        return True
    else :
        return False
 
    

seq=[1,2,3,4,5,6,7,8,9,10]
print(my_filter(is_even,seq))

edited Jun 20 '20 at 09:12

Community

1
1

answered Dec 20 '19 at 13:38

Yogananda Sai

1

Output will be [2, 4, 6, 8, 10].Here the address of is_even and func is same. – Yogananda Sai Dec 20 '19 at 13:39

score 0 · Answer 3 · answered Apr 26 '20 at 09:18

0

Custom filter function in python:

def myfilter(fun, data):
    return [i for i in data if fun(i)]

answered Apr 26 '20 at 09:18

Biman Pal

391
4
9

score 0 · Answer 4 · answered Nov 18 '11 at 02:06

0

I like the answer from Óscar López but you should also learn to use the existing Python filter function:

>>> def myfilter(tgt, seq):
        return filter(lambda x: x!=tgt, seq)

>>> myfilter(1, [1,2,1])
[2]

answered Nov 18 '11 at 02:06

Raymond Hettinger

216,523
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Python: Creating a filter function

4 Answers4

Custom Filter Function