Deleting list elements based on condition

Question

I have a list of lists: [word, good freq, bad freq, change_status]

list_1 = [['good',100, 20, 0.2],['bad', 10, 0, 0.0],['change', 1, 2, 2]] 

I would like to delete from the list all elements which don't satisfy a condition.

So if change_status > 0.3 and bad_freq < 5 then I would like to delete that the elements corresponding to it.

So the list_1 would be modified as,

list_1 = [['good',100, 20, 0.2],['bad', 10, 0, 0.0]] 

How do I selective do that?

Answer 1

list_1 = [['good',100, 20, 0.2],['bad', 10, 0, 0.0],['change', 1, 2, 2]] list_1 = [item for item in list_1 if item[2] >= 5 or item[3] >= 0.3] 

You can also use if not (item[2] < 5 and item[3] < 0.3) for the condition if you want.

Answer 2

Use the filter function with an appropriate function.

list_1 = filter(lambda x: x[3] <= 0.3 and x[2] < 5, list_1) 

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Demo:

In [1]: list_1 = [['good',100, 20, 0.2],['bad', 10, 0, 0.0],['change', 1, 2, 2]] In [2]: filter(lambda x: x[3] <= 0.3 and x[2] < 5, list_1) Out[2]: [['bad', 10, 0, 0.0]] 

Note that good doesn't satisfy your condition (20 < 5 is false) even though you said so in your question!

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If you have many elements you might want to use the equivalent function from itertools:

from itertools import ifilter filtered = ifilter(lambda x: x[3] <= 0.3 and x[2] < 5, list_1)