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I have implemented a lambda function to sort a list. now i want to remove all the negative objects from the list by using lambda functions . 

dto_list.sort(key=lambda x: x.count, reverse=True)

any one know a way to write the lambda expression to do it? I could not find a proper tutorial

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Do you have to use a lambda? Usually they are unnecessary and make code less readable. – jamylak May 16 '12 at 7:43
    
yep have to use lambda – Evlikosh Dawark May 16 '12 at 7:44
    
FYI the pythonic way to do the above is sorted(dto_list, key=operator.attrgetter("count"), reverse=True) – katrielalex May 16 '12 at 8:10
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Not very pythonic but here is how to do it with a lambda

>>> L = list(range(-10,10))
>>> L
[-10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> filter(lambda x: x >= 0, L)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>>

Most people would use a list comprehension

>>> [x for x in L if x >= 0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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Hey thank you very much – Evlikosh Dawark May 16 '12 at 7:50
    
any one know python standards for list operations ? whether to use lambda functions? what are the good practices ? – Kalanamith May 16 '12 at 8:08
3  
@Kalanamith: The "standard" is to use whatever is shortest and easiest to understand. Sometimes that will be a list comprehension; sometimes it will be itertools; sometimes that will be a lambda function used with map(), filter(), or reduce(). You get to make the call as to which one is better for your application. – Li-aung Yip May 16 '12 at 8:13

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