removing all instances of a certain value from a list

[Lee Sander]

Hi,
I have a float array ( eg [-1.3, 1.22, 9.2, None, 2.3] ) but there are
many missing vlaues which are represented as None. I would like to
remove all such instances in one go.
There is a remove function but it removes only the first instance, is
there a delete/remove all function?
thanks

[=?ISO-8859-1?Q?BJ=F6rn_Lindqvist?=]

Re: removing all instances of a certain value from a list

On Wed, Mar 19, 2008 at 10:28 PM, Lee Sander <lesande@gmail. comwrote:

Hi,
I have a float array ( eg [-1.3, 1.22, 9.2, None, 2.3] ) but there are
many missing vlaues which are represented as None. I would like to
remove all such instances in one go.
There is a remove function but it removes only the first instance, is
there a delete/remove all function?
thanks

If it is ok to copy the list instead of mutating it, use a list comprehension:

>>L = [-1.3, 1.22, 9.2, None, 2.3]
>>[x for x in L if x is not None]

[-1.3, 1.22, 9.1999999999999 993, 2.2999999999999 998]

--
mvh Björn

[Hrvoje Niksic]

Re: removing all instances of a certain value from a list

Lee Sander <lesande@gmail. comwrites:

Hi,
I have a float array ( eg [-1.3, 1.22, 9.2, None, 2.3] ) but there are
many missing vlaues which are represented as None. I would like to
remove all such instances in one go.
There is a remove function but it removes only the first instance, is
there a delete/remove all function?

No, but you can easily simulate it using, for example:

lst[:] = (el for el in lst if el is not None)

[r.grimm@science-computing.de]

Re: removing all instances of a certain value from a list

On Mar 19, 11:28 pm, Lee Sander <lesa...@gmail. comwrote:

Hi,
I have a float array ( eg [-1.3, 1.22, 9.2, None, 2.3] ) but there are
many missing vlaues which are represented as None. I would like to
remove all such instances in one go.
There is a remove function but it removes only the first instance, is
there a delete/remove all function?
thanks

You can also do it with the filter function.

>>a= [-1.3, 1.22, 9.2, None, 2.3]
>>a=filter ( lambda b: b != None, a)
>>print a

[-1.3, 1.22, 9.1999999999999 993, 2.2999999999999 998]

Greetings Rainer

[bearophileHUGS@lycos.com]

Re: removing all instances of a certain value from a list

r.gr...@science-computing.de:

>a=filter ( lambda b: b != None, a)

With None it's better to use is/not is instead of ==/!=

Bye,
bearophile