Re: why does list's .remove() does not return an object?

[Abdur-Rahmaan Janhangeer]

ah there's no return question then

that precisely returned the discussion to the first answer

Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 23:35 Tobiah,  wrote:

> On 05/17/2018 09:25 AM, Ned Batchelder wrote:
> > On 5/17/18 11:57 AM, Abdur-Rahmaan Janhangeer wrote:
> >> x = [0,1]
> >> x.remove(0)
> >> new_list = x
>
> Just call the original list 'new_list' to begin with.
>
>new_list = [0, 1]
>new_list.remove(0)
>
>
> There you are!
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Aw: Re: why does list's .remove() does not return an object?

[Karsten Hilbert]

>new_list = list(x.remove(0))
>new_list = x.remove(0)[:]

Please disregard :)

kh
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Re: Re: why does list's .remove() does not return an object?

[Ian Kelly]

On Thu, May 17, 2018 at 3:27 PM, Karsten Hilbert
 wrote:
>> On 5/17/18 11:57 AM, Abdur-Rahmaan Janhangeer wrote:
>> > x = [0,1]
>> > x.remove(0)
>> > new_list = x
>> >
>> > instead i want in one go
>> >
>> > x = [0,1]
>> > new_list = x.remove(0) # here a way for it to return the modified list by
>> > adding a .return() maybe ?
>>
>> There isn't a way to do that in one line.
>
>new_list = list(x.remove(0))
>new_list = x.remove(0)[:]
>
> ?
>
> No one said x can't be modified, only that new_list is
> to contain the modified list after one line of code :)

Did you actually run either of those?
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Aw: Re: why does list's .remove() does not return an object?

[Karsten Hilbert]

> On 5/17/18 11:57 AM, Abdur-Rahmaan Janhangeer wrote:
> > x = [0,1]
> > x.remove(0)
> > new_list = x
> >
> > instead i want in one go
> >
> > x = [0,1]
> > new_list = x.remove(0) # here a way for it to return the modified list by
> > adding a .return() maybe ?
> 
> There isn't a way to do that in one line.

   new_list = list(x.remove(0))
   new_list = x.remove(0)[:]

?

No one said x can't be modified, only that new_list is
to contain the modified list after one line of code :)

kh
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Re: why does list's .remove() does not return an object?

[Tobiah]

On 05/17/2018 09:25 AM, Ned Batchelder wrote:

On 5/17/18 11:57 AM, Abdur-Rahmaan Janhangeer wrote:

x = [0,1]
x.remove(0)
new_list = x


Just call the original list 'new_list' to begin with.

  new_list = [0, 1]
  new_list.remove(0)


There you are!
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Re: why does list's .remove() does not return an object?

[David Stanek]

On 17-May-2018 12:37, Ned Batchelder wrote:
> On 5/17/18 12:28 PM, Dan Strohl via Python-list wrote:
> > On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:
> > > I don't understand what this would return? x? You already have x.  Is
> > > it meant to make a copy? x has been mutated, so I don't understand the
> > > benefit of making a copy of the 1-less x.  Can you elaborate on the
> > > problem you are trying to solve?
> > >
> > > --Ned.
> > >
> > >
> > > assignment to another var
> > >
> > Though I don’t know what the OP was specifically looking for I could see a 
> > benefit to returning the item deleted.
>
> Notice that this is not the thing the OP wanted returned.  I believe they
> are looking to return the list, not the item.
>

I'm guessing that they want to be able to do some sort of method
chaining like:

  the_list.remove(x).remove(y)

Although the clarifying example was contrived and confusing. A more
concrete example would be greatly appreciated.

-- 
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twitter: https://twitter.com/dstanek
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Re: why does list's .remove() does not return an object?

[Ned Batchelder]

On 5/17/18 12:28 PM, Dan Strohl via Python-list wrote:

On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:

I don't understand what this would return? x? You already have x.  Is
it meant to make a copy? x has been mutated, so I don't understand the
benefit of making a copy of the 1-less x.  Can you elaborate on the
problem you are trying to solve?

--Ned.


assignment to another var


Though I don’t know what the OP was specifically looking for I could see a 
benefit to returning the item deleted.


Notice that this is not the thing the OP wanted returned.  I believe 
they are looking to return the list, not the item.


--Ned.
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RE: why does list's .remove() does not return an object?

[Dan Strohl via Python-list]

On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:
> I don't understand what this would return? x? You already have x.  Is 
> it meant to make a copy? x has been mutated, so I don't understand the 
> benefit of making a copy of the 1-less x.  Can you elaborate on the 
> problem you are trying to solve?
>
> --Ned.
>
>
> assignment to another var
>

Though I don’t know what the OP was specifically looking for I could see a 
benefit to returning the item deleted.

So, lets take as an example I have an object like:

class ListItem(object):
def __init__(self, key, data):
self.key = key
self.data = data
def __eq__(other):
return other == self.key

and I do something like:

i1 = ListItem('hello', 'foobar')
l2 = ListItem('goodby', 'snafu')

l = [i1, i2]

So, lets say I have a need where I want to do something like a remove, but I 
also want to be able to get the .data variable from the object I am removing, 
it would be nice to be able to simply do

x = l.remove('hello')
print(x.data)

Yes, I could do a index/pop to get this, or I could keep a separate dict of the 
objects as well for lookups, or a number of other techniques, but it would be 
easier to simply get it back during the remove().

Dan Strohl

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Re: why does list's .remove() does not return an object?

[Ned Batchelder]

On 5/17/18 11:57 AM, Abdur-Rahmaan Janhangeer wrote:

x = [0,1]
x.remove(0)
new_list = x

instead i want in one go

x = [0,1]
new_list = x.remove(0) # here a way for it to return the modified list by
adding a .return() maybe ?


There isn't a way to do that in one line.  I often find myself splitting 
long statements into more, shorter, statements to express myself more 
clearly.


I don't know if you have a real piece of code in mind, so I don't know 
if you can tell us:  why is it useful to have another variable referring 
to the same list?


--Ned.


Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 19:54 Alexandre Brault,  wrote:


On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:

I don't understand what this would return? x? You already have x.  Is it
meant to make a copy? x has been mutated, so I don't understand the

benefit

of making a copy of the 1-less x.  Can you elaborate on the problem you

are

trying to solve?

--Ned.


assignment to another var


You already have access to the list before removal, the list after
removal and the element to be removed.

Do need a copy of the list before removing x?

old_list = list[:]
list.remove(x)

Do you need the list after removing x?

list.remove(x)  # list is the modified list

Do you need x?

list.remove(x)  # x is x

What else would need to be assigned to another var?
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Re: why does list's .remove() does not return an object?

[Abdur-Rahmaan Janhangeer]

x = [0,1]
x.remove(0)
new_list = x

instead i want in one go

x = [0,1]
new_list = x.remove(0) # here a way for it to return the modified list by
adding a .return() maybe ?

Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 19:54 Alexandre Brault,  wrote:

>
> On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:
> > I don't understand what this would return? x? You already have x.  Is it
> > meant to make a copy? x has been mutated, so I don't understand the
> benefit
> > of making a copy of the 1-less x.  Can you elaborate on the problem you
> are
> > trying to solve?
> >
> > --Ned.
> >
> >
> > assignment to another var
> >
> You already have access to the list before removal, the list after
> removal and the element to be removed.
>
> Do need a copy of the list before removing x?
> >>> old_list = list[:]
> >>> list.remove(x)
>
> Do you need the list after removing x?
> >>> list.remove(x)  # list is the modified list
>
> Do you need x?
> >>> list.remove(x)  # x is x
>
> What else would need to be assigned to another var?
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>
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Re: why does list's .remove() does not return an object?

[Alexandre Brault]

On 2018-05-17 11:26 AM, Abdur-Rahmaan Janhangeer wrote:
> I don't understand what this would return? x? You already have x.  Is it
> meant to make a copy? x has been mutated, so I don't understand the benefit
> of making a copy of the 1-less x.  Can you elaborate on the problem you are
> trying to solve?
>
> --Ned.
>
>
> assignment to another var
>
You already have access to the list before removal, the list after
removal and the element to be removed.

Do need a copy of the list before removing x?
>>> old_list = list[:]
>>> list.remove(x)

Do you need the list after removing x?
>>> list.remove(x)  # list is the modified list

Do you need x?
>>> list.remove(x)  # x is x

What else would need to be assigned to another var?
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Re: why does list's .remove() does not return an object?

[Abdur-Rahmaan Janhangeer]

On Thu, 17 May 2018, 18:55 Ned Batchelder,  wrote:

> On 5/17/18 4:23 AM, Abdur-Rahmaan Janhangeer wrote:
>
> if then a more convenient way might be found to naturally remove and
> return the list
>
> maybe it was not included as one might want to remove the list only
>
> x = [1]
> x.remove(1)
>
> as opposed to
>
> x = [1]
> x.remove(1)
> new_list = x
>
> i was looking for like
>
> x = [1]
> x.remove(1).return()
>
>
> I don't understand what this would return? x? You already have x.  Is it
> meant to make a copy? x has been mutated, so I don't understand the benefit
> of making a copy of the 1-less x.  Can you elaborate on the problem you are
> trying to solve?
>
> --Ned.
>
>
assignment to another var

>
>
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Re: why does list's .remove() does not return an object?

[Ned Batchelder]

On 5/17/18 4:23 AM, Abdur-Rahmaan Janhangeer wrote:
if then a more convenient way might be found to naturally remove and 
return the list


maybe it was not included as one might want to remove the list only

x = [1]
x.remove(1)

as opposed to

x = [1]
x.remove(1)
new_list = x

i was looking for like

x = [1]
x.remove(1).return()


I don't understand what this would return? x? You already have x. Is it 
meant to make a copy? x has been mutated, so I don't understand the 
benefit of making a copy of the 1-less x.  Can you elaborate on the 
problem you are trying to solve?


--Ned.

(PS: bottom-posting (adding your response below the text you are 
responding to) will make the conversation easier to follow...)




ps. list is was demo illustrative var

Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 07:01 Ned Batchelder, > wrote:


On 5/16/18 10:41 PM, Abdur-Rahmaan Janhangeer wrote:
> why is x = list.remove(elem) not return the list?
>
>
Methods in Python usually do one of two things: 1) mutate the
object and
return None; or 2) leave the object alone and return a new
object.  This
helps make it clear which methods mutate and which don't. Since
.remove
mutates the list, it returns None.

--Ned.
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Re: why does list's .remove() does not return an object?

[Jach Fong]

Abdur-Rahmaan Janhangeer at 2018/5/17 PM 04:23 wrote:

if then a more convenient way might be found to naturally remove and return
the list

maybe it was not included as one might want to remove the list only

x = [1]
x.remove(1)

as opposed to

x = [1]
x.remove(1)
new_list = x


IMO, this way is more flexible on its usage and avoid
a redundant copy.

--Jach



i was looking for like

x = [1]
x.remove(1).return()

ps. list is was demo illustrative var

Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 07:01 Ned Batchelder,  wrote:


On 5/16/18 10:41 PM, Abdur-Rahmaan Janhangeer wrote:

why is x = list.remove(elem) not return the list?



Methods in Python usually do one of two things: 1) mutate the object and
return None; or 2) leave the object alone and return a new object.  This
helps make it clear which methods mutate and which don't.  Since .remove
mutates the list, it returns None.

--Ned.
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Re: why does list's .remove() does not return an object?

[Abdur-Rahmaan Janhangeer]

if then a more convenient way might be found to naturally remove and return
the list

maybe it was not included as one might want to remove the list only

x = [1]
x.remove(1)

as opposed to

x = [1]
x.remove(1)
new_list = x

i was looking for like

x = [1]
x.remove(1).return()

ps. list is was demo illustrative var

Abdur-Rahmaan Janhangeer
https://github.com/Abdur-rahmaanJ

On Thu, 17 May 2018, 07:01 Ned Batchelder,  wrote:

> On 5/16/18 10:41 PM, Abdur-Rahmaan Janhangeer wrote:
> > why is x = list.remove(elem) not return the list?
> >
> >
> Methods in Python usually do one of two things: 1) mutate the object and
> return None; or 2) leave the object alone and return a new object.  This
> helps make it clear which methods mutate and which don't.  Since .remove
> mutates the list, it returns None.
>
> --Ned.
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Re: why does list's .remove() does not return an object?

[jladasky]

On Wednesday, May 16, 2018 at 7:42:01 PM UTC-7, Abdur-Rahmaan Janhangeer wrote:
> why is x = list.remove(elem) not return the list?
> 
> Abdur-Rahmaan Janhangeer
> https://github.com/Abdur-rahmaanJ

1) If you are naming your list "list," you're asking for trouble.  Shadowing 
builtin names is risky.  Ten years ago I named a variable "max".  Oops.

2) list.remove() operates in-place.  Would you expect it to return a copy?  
Making that copy could potentially use a lot of memory and time.

3) If you do want a copy, construct it from two slices of your original list.  
Let's say the element you want to remove is at position 6.  Then:

new_list = old_list[:6] + old_list[7:]


3)
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Re: why does list's .remove() does not return an object?

[Ned Batchelder]

On 5/16/18 10:41 PM, Abdur-Rahmaan Janhangeer wrote:

why is x = list.remove(elem) not return the list?


Methods in Python usually do one of two things: 1) mutate the object and 
return None; or 2) leave the object alone and return a new object.  This 
helps make it clear which methods mutate and which don't.  Since .remove 
mutates the list, it returns None.


--Ned.
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