how to append to list in list comprehension

[Sayth Renshaw]

I have a list of lists of numbers like this excerpt.

['0', '0', '0', '0']
['0', '0', '0', '0']
['0', '0', '0', '0']
['0', '0', '0', '0']
['0', '0', '0', '0']
['0', '0', '0', '0']
['7', '2', '1', '0', '142647', '00']
['7', '2', '0', '1', '87080', '00']
['6', '1', '1', '1', '51700', '00']
['4', '1', '1', '0', '36396', '00']

I want to go threw and for each index error at [4] append a 0.

I have called the lists fups.

p = re.compile('\d+')
fups = p.findall(nomattr['firstup'])
[x[4] for x in fups if IndexError fups.append(0)]
print(fups)

Unsure why I cannot use append in this instance, how can I modify to acheive desired output?

Desired Output
['0', '0', '0', '0', '0']
['0', '0', '0', '0', '0']
['0', '0', '0', '0', '0']
['0', '0', '0', '0', '0']
['0', '0', '0', '0', '0']
['0', '0', '0', '0', '0']
['7', '2', '1', '0', '142647', '00']
['7', '2', '0', '1', '87080', '00']
['6', '1', '1', '1', '51700', '00']
['4', '1', '1', '0', '36396', '00']

Thanks

Sayth