list iteration if statement

alex goretoy aleksandr.goretoy at gmail.com
Sat Jan 3 03:47:42 CET 2009


v should have ['3','4','1'] sorry if I made it confusing.

On Sat, Jan 3, 2009 at 2:43 AM, alex goretoy <aleksandr.goretoy at gmail.com>wrote:

> rather, how do I suppress the output of the list with all None in it?
>
> >>> l=[['3'], ['0', '4'], ['0', '1'], ['0']]
> >>> v=[]
> >>> [[v.append(j)for j in i if j != "0"] for i in l]
> [[None], [None], [None], []]
> >>> v
> ['39', '32', '1']
>
> >>>
>
> On Sat, Jan 3, 2009 at 2:38 AM, alex goretoy <aleksandr.goretoy at gmail.com>wrote:
>
>> Thank you Steve and MRAB,
>>
>> This is what I was looking for:
>>
>>  [[v.append(j) for j in i if j != 0] for i in self.value]
>>
>> the value is actually stored as a string so I would need to check if it is
>> "0". I do have one more question about list comprehension though. After
>> doing this I get an unwanted list of None how do I make it disappear or not
>> return this list. Would I have to be modifying it in place for this to
>> happen? Wouldn't modifying it in place potentially overwrite some other
>> values? I just don't want it to return [[None], [None, None], [None, None],
>> [None]]
>>
>> You guys rock, thanks for helping me learn python.
>>
>>
>> On Sat, Jan 3, 2009 at 2:09 AM, Steve Holden <steve at holdenweb.com> wrote:
>>
>>> alex goretoy wrote:
>>> > Hello All,
>>> >
>>> > I'm doing this in my code
>>> >
>>> > [[v.append(j) for j in i] for i in self.value]
>>> >
>>> > if works and all, but I need to add a if statement in the mix. Can't
>>> > seem to remember the syntax to do so and everything I've tried seems to
>>> > fail. How do I add a check to see if j is not int("0") then append to v
>>> > list? Thank you in advance. -A
>>>
>>> Who, tiger. It "works" for a value of "works" that involves creating two
>>> lists. One is the one you want, referenced by v, and the other is the
>>> value if the list comprehension, which will be a list full of lists of
>>> all the None values returned by those append() calls. But I presume you
>>> are throwing that second list away ...
>>>
>>> See, a list comprehension is intended to create a list. So what you
>>> should have used (assuming v was the empty list before you started) was
>>>
>>> v = [[j for j in i] for i in self.value]
>>>
>>> Further, when you say 'j is not int("0")', do you actually mean that a
>>> is not in integer with the value 0? Assuming you do then what you need is
>>>
>>> v = [[j for j in i if not j] for i in self.value]
>>>
>>> or, more pedantically
>>>
>>> v = [[j for j in i if j==0] for i in self.value]
>>>
>>> regards
>>>  Steve
>>> --
>>> Steve Holden        +1 571 484 6266   +1 800 494 3119
>>> Holden Web LLC              http://www.holdenweb.com/
>>>
>>> --
>>> http://mail.python.org/mailman/listinfo/python-list
>>>
>>
>>
>>
>> --
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>>
>
>
>
> --
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>



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