Removing elements from a list of a list

Question

I have the data below, which is a list of lists. I would like to remove the last two elements from each list, leaving only the first three elements. I have tried list.append(), list.pop() but can't seem to get them to work. I guess it is not possible to remove elements from a list in a for loop, which is what I had been previously trying. What is the best way to go about this?

data = [(datetime.datetime(2013, 11, 12, 19, 24, 50), u'78:E4:00:0C:50:DF', u' 8', u'Hon Hai Precision In', u''), (datetime.datetime(2013, 11, 12, 19, 24, 50), u'78:E4:00:0C:50:DF', u' 8', u'Hon Hai Precision In', u''), (datetime.datetime(2013, 11, 12, 19, 24, 48), u'9C:2A:70:69:81:42', u' 5', u'Hon Hai Precision In 12:', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'00:1E:4C:03:C0:66', u' 9', u'Hon Hai Precision In', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'20:C9:D0:C6:8F:15', u' 8', u'Apple', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'68:5D:43:90:C8:0B', u' 11', u'Intel Orate', u' MADEGOODS'), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'68:96:7B:C1:76:90', u' 15', u'Apple', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'68:96:7B:C1:76:90', u' 15', u'Apple', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'04:F7:E4:A0:E1:F8', u' 32', u'Apple', u''), (datetime.datetime(2013, 11, 12, 19, 24, 47), u'04:F7:E4:A0:E1:F8', u' 32', u'Apple', u'')]

Actually you don't have a list of lists, you have a list of tuples — Christian Tapia
– Christian Tapia, Commented Nov 13, 2013 at 3:03

iruvar · Accepted Answer · 2013-11-13 03:00:15Z

4

You could use a list comprehension and create a new list of lists with 2 elements removed from each sublist

data = [x[:-2] for x in data]

answered Nov 13, 2013 at 3:00

iruvar

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3 Comments

metersk Over a year ago

awesome! thank you. i knew it was simpler than what i had been trying!

user2555451 Over a year ago

Why not just data = [x[:-2] for x in data]?

iruvar Over a year ago

@iCodez, done. I wrote it out in 2 steps for the sake of elaboration but I guess it just makes me look like a dummy ;-)

John La Rooy · Accepted Answer · 2013-11-13 03:16:35Z

As @christian says, you have a list of tuple, as opposed to list. The distinction is significant here as tuple is immutable. You can convert to list of list like this

data = map(list, data)

Now you can mutate each item as you iterate over it

for item in data: del item[-2:]

In your case the list comprehension is better because it works on your list of tuple equally well.

just curious on the indicators or how i was supposed to know that i had a list of tuples as opposed to a list of a list??

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