Extracting a changeable string from a list and insertion in Python

Question

I have a list that looks like this:

['2    19   2839475239874 hda']

I need to extract the hda from the end. However, the hda may not always be the last chunk, hda may not always be only 3 letters (it could be 4 or 5, and it could include numbers); BUT it will always start with the letter 'h'.

After the hda is successfully extracted, I then need to insert that chunk into a dd command. That looks like this:

dd if=/dev/zero of=/dev/hda bs=512 count=1

But if the hda could be different each time I run the dd command, I need a way to have the 'hda' part of the dd command changeable.

Sorry if this is confusing, I am a beginner and confused myself! I've tried using startswith for extraction, but can't even get past there!

Answer 1

Simply like so:

lst = ['2    19   2839475239874 hda']

# Extracting the device part
dev = filter(lambda s: s[0] is 'h', lst[0].split())[0]

# Inserting it
cmd = 'dd if=/dev/zero of=/dev/{0} bs=512 count=1'.format(dev)

You will want to check the case where you don't have any h-word in your list though.

Answer 2

>>> thelist = ['2    19   2839475239874 hda']
>>> [item for item in thelist[0].split() if item[0] == 'h'][0]
'hda'