Change position of a line with a specific string, using python

I am new to coding, trying to find a simple python code for re-arranging some lines. Lines have specific string to select. Those lines with this specific string need to be moved.

Original File content:

element = element1
attribute1 = value1last
attribute2 = value2
attribute3 = value3

element =element2
attribute1 = value1last
attribute2 = value2
attribute3 = value3

Note: the attribute line with “last” in it, this whole line should go to the end of each element’s attribute list.

New file format:

element = element1
attribute2 = value2
attribute3 = value3
attribute1 = value1last

element =element2
attribute2 = value2
attribute3 = value3
attribute1 = value1last

Appreciate any help on this.

Answer

Try this:

with open('input.txt', 'r') as f:
    data = f.read().splitlines()
#print(data)

sep_lists = [[]]
for i in data:
    if not i:
        sep_lists.append([])
    else:
        sep_lists[-1].append(i)

#print(sep_lists)
for lists in sep_lists:
    for idx, elem in enumerate(lists):
        if 'last' in elem:
            last = idx
    lists.append(lists.pop(last))

with open('output.txt', 'w') as f:
    for lists in sep_lists:
        f.write('n'.join(lists) + 'nn')