Find a sublist full of given item and replace it

Question

Assume I have the list following

[1, 1, 1, 1, 2, 1, 3, 2, 1, 2, 2, 1, 2, 2, 1, 1, 1, 1, 3, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 2, 1, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 3, 1, 1, 2, 1, 3, 2, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 3, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 2, 1, 1, 2, 5, 4, 3, 1, 2, 2, 1, 1, 1, 1, 2, 3, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 1, 2, 1, 1, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 3, 1, 1, 3, 2, 1, 1, 2, 3, 1, 2, 2, 2, 1, 2, 2, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 1, 4, 2, 1, 1, 1, 2, 1, 2, 2, 2, 2, 1, 2, 1, 1, 3, 3, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 3, 1, 1, 1, 4, 1, 1, 1, 1, 1, 3, 1, 2, 1, 2, 3, 1, 1, 2, 2, 1, 4, 1, 2, 1, 1, 1, 3, 1, 1, 3, 2, 1, 2, 2, 1, 2, 1, 2, 3, 1, 1, 1, 3, 2, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 3, 1, 1, 4, 1, 2, 1, 1, 3, 3, 4, 2, 2, 5, 1, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 4, 3, 1, 1, 1, 3, 1, 1, 1, 2, 1, 3, 4, 2, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 3, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 4, 1, 1, 3, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 1, 1, 1, 5, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 3, 2, 2, 1, 3, 4, 2, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 1, 3, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 3, 1, 4, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 5, 1, 1, 1, 2, 1, 1, 1, 2, 1, 4, 1, 3, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 3, 1, 2, 1, 2, 2, 1, 1, 1, 1, 2, 4, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 1, 4, 2, 1, 1, 3, 3, 2, 2, 1, 1, 1, 4, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 4, 1, 3, 2, 2, 1, 1, 3, 1, 2, 2, 1, 2, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 2, 2, 4, 3, 4, 2, 1, 1, 1, 1, 1, 2, 2, 2, 3, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 4, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 2, 1, 2, 2, 3, 4, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 4, 2, 1, 3, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2]

What I want to do is to compose all the same values following each other to strings. For instance

[1,1,1,1,1,1,1,2,3,1,1,1,2,2,2,2,3,3,4,5,1,1]

should be composed as the following

["1x7",2,3,"1x3","2x4","3x2",4,5,"1x2"]

I reckon multiplying each of the following values and checking if their product is different than 1,4,9,16,25 can work up to some point but when it comes to bigger lists, it won't be enough.

Is there a shortcut that python provides?

Answer 1

You can use itertools.groupby to collect consecutive runs of the same value.

from itertools import groupby
def condense(group):
    values = list(group)
    if len(values) > 1:
        return '{}x{}'.format(values[0], len(values))
    else:
        return values[0]

You can use this function in a list comprehensino

>>> data = [1, 1, 1, 1, 2, 1, 3, 2, 1, 2, 2, 1, 2, 2, 1, 1, 1, 1, 3, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 2, 1, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 3, 1, 1, 2, 1, 3, 2, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 1, 3, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 2, 1, 1, 2, 5, 4, 3, 1, 2, 2, 1, 1, 1, 1, 2, 3, 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 1, 2, 1, 1, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 3, 1, 1, 3, 2, 1, 1, 2, 3, 1, 2, 2, 2, 1, 2, 2, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 1, 4, 2, 1, 1, 1, 2, 1, 2, 2, 2, 2, 1, 2, 1, 1, 3, 3, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 3, 1, 1, 1, 4, 1, 1, 1, 1, 1, 3, 1, 2, 1, 2, 3, 1, 1, 2, 2, 1, 4, 1, 2, 1, 1, 1, 3, 1, 1, 3, 2, 1, 2, 2, 1, 2, 1, 2, 3, 1, 1, 1, 3, 2, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 3, 1, 1, 4, 1, 2, 1, 1, 3, 3, 4, 2, 2, 5, 1, 1, 1, 1, 1, 1, 1, 1, 3, 4, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 4, 3, 1, 1, 1, 3, 1, 1, 1, 2, 1, 3, 4, 2, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 3, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 4, 1, 1, 3, 4, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 1, 1, 1, 5, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 4, 2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 3, 2, 2, 1, 3, 4, 2, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 4, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 1, 3, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 3, 1, 4, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 5, 1, 1, 1, 2, 1, 1, 1, 2, 1, 4, 1, 3, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 3, 1, 2, 1, 2, 2, 1, 1, 1, 1, 2, 4, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 1, 4, 2, 1, 1, 3, 3, 2, 2, 1, 1, 1, 4, 3, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 4, 1, 3, 2, 2, 1, 1, 3, 1, 2, 2, 1, 2, 2, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 2, 2, 4, 3, 4, 2, 1, 1, 1, 1, 1, 2, 2, 2, 3, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 4, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 2, 1, 2, 2, 3, 4, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 3, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 2, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 4, 2, 1, 3, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2]
>>> [condense(g) for k,g in groupby(data)]
['1x4', 2, 1, 3, 2, 1, '2x2', 1, '2x2', '1x4', 3, '1x2', '2x2', 1, 2, '1x2', 3, '1x4', '2x2', 1, 2, 1, 2, 1, 2, '1x2', 3, '1x7', 2, 1, 2, '1x8', 2, '1x4', '2x2', 3, '1x2', 2, 1, 3, 2, '1x2', 2, 1, '2x2', '1x13', 2, '1x3', '2x2', '1x2', '2x2', '1x3', '2x2', '1x4', 2, '1x3', 2, '1x2', 2, 1, 3, 2, '1x6', 2, '1x2', 3, '1x5', 3, '1x2', 3, '1x2', 2, '1x2', 2, 5, 4, 3, 1, '2x2', '1x4', 2, 3, '1x2', '2x6', 1, 2, '1x6', 2, 3, '1x2', 2, 1, 2, '1x2', 2, 3, '1x8', 4, '1x2', 2, 3, '1x2', 3, 2, '1x2', 2, 3, 1, '2x3', 1, '2x2', '1x3', 2, 3, '1x6', 4, 2, '1x3', 2, 1, '2x4', 1, 2, '1x2', '3x2', '1x2', 2, '1x3', '2x2', '1x2', 2, 3, '1x3', 4, '1x5', 3, 1, 2, 1, 2, 3, '1x2', '2x2', 1, 4, 1, 2, '1x3', 3, '1x2', 3, 2, 1, '2x2', 1, 2, 1, 2, 3, '1x3', 3, 2, 1, 2, '1x2', '2x2', '1x10', '2x2', '1x3', '2x2', '1x2', 2, '1x2', 2, '1x3', 3, '1x3', 2, '1x2', 2, '1x2', 2, '1x2', 3, '1x2', 3, '1x2', 4, 1, 2, '1x2', '3x2', 4, '2x2', 5, '1x8', 3, 4, '1x6', 2, 1, 2, '1x2', 4, 3, '1x3', 3, '1x3', 2, 1, 3, 4, '2x3', '1x2', '2x2', '1x6', 2, 3, '1x2', 2, 3, '1x2', '2x2', '1x2', 2, '1x6', 2, '1x2', 4, '1x2', 3, 4, '1x20', '2x2', 1, '2x2', 1, 2, 1, '2x3', 1, '2x2', '1x3', 5, '1x2', 3, '1x7', '2x2', 3, 4, 2, '1x5', 3, '1x4', 3, '2x2', 1, 3, 4, 2, '1x2', 2, 1, 2, 1, 3, 1, 2, '1x5', 2, '1x3', 2, '1x5', 2, '1x3', 3, 2, '1x2', 4, '1x3', 2, '1x8', 2, 1, 3, '1x2', 3, '1x2', '2x2', '1x2', 2, '1x4', 2, '1x2', '2x2', '1x4', 2, 1, 2, '1x2', 2, '1x4', '2x2', 3, 1, 4, '1x2', 2, '1x6', 2, '1x2', 2, 5, '1x3', 2, '1x3', 2, 1, 4, 1, '3x2', '1x3', 3, '1x6', 2, 1, 2, '1x15', 2, '1x4', '2x2', '1x9', 2, '1x8', 2, '1x3', 2, '1x3', 2, 1, '2x2', 1, '2x2', '1x2', '2x2', 3, 1, 2, 1, '2x2', '1x4', 2, 4, '1x4', '2x2', '1x3', 2, '1x2', 2, '1x10', 2, '1x4', 2, 1, 3, 2, '1x11', 2, '1x5', 2, '1x2', '2x2', '1x3', 2, '1x2', 2, 1, 3, 1, 2, '1x2', 4, 2, '1x2', '3x2', '2x2', '1x3', 4, 3, 2, '1x10', 2, '1x3', '2x2', '1x2', '2x2', '1x6', '2x2', '1x2', 2, '1x2', 2, '1x2', 3, '1x3', 2, '1x3', '2x2', '1x2', 2, '1x2', 2, '1x2', 2, '1x2', 3, '1x2', 2, '1x2', '2x2', '1x4', '2x2', '1x3', 4, 1, 3, '2x2', '1x2', 3, 1, '2x2', 1, '2x2', 3, '1x16', '2x2', '1x7', 3, '1x5', 2, '1x5', 2, '1x5', '2x2', '1x4', 2, '1x2', 2, '1x2', 3, '1x3', 3, '1x4', '2x2', 4, 3, 4, 2, '1x5', '2x3', 3, '1x4', 2, '1x5', 2, '1x4', 2, '1x2', 2, 1, 2, 4, '1x4', '2x2', '1x2', 2, '1x4', 3, '1x3', 3, '1x4', 2, 1, '2x2', 3, 4, '1x2', '2x2', '1x8', 3, 2, '1x2', 3, '1x33', 2, '1x2', 2, '1x3', 2, 3, '1x5', 2, '1x6', 2, '1x5', 2, '1x2', 2, 1, '2x2', '1x5', 2, '1x2', 2, '1x8', 2, '1x3', '2x2', '1x2', 2, '1x9', 3, 2, '1x5', 2, '1x7', 3, '2x2', '1x5', 2, '1x3', 2, '1x10', 3, 1, 2, '1x3', '2x2', '1x2', 2, '1x2', 2, 4, 2, 1, 3, '1x2', 2, '1x6', 2]

Answer 2

If you just want this data to take less space, you can use a dictionary with the items as keys and number of their appearance in the list as values. I used set to remove duplicates and then created the dictionary.

a = [1,1,1,1,1,1,1,2,3,1,1,1,2,2,2,2,3,3,4,5,1,1]
d = {i:a.count(i) for i in set(a)}
print(d)

output:

{1: 12, 2: 5, 3: 3, 4: 1, 5: 1}

Reading from and writing to a dictionary is a lot easier than a string in that form. You can also simply store a dictionary as JSON file.

UPDATE :

So if the sequence of the elements is important. You can do like this:

a = [1,1,1,1,1,1,1,2,3,1,1,1,2,2,2,2,3,3,4,5,1,1]
b = []
count = 1
for i in range(1,len(a)):
    if a[i-1] != a[i]:
        b.append((a[i-1],count))
        count = 0
    count += 1
b.append((a[-1],count))
print(b)

output:

[(1, 7), (2, 1), (3, 1), (1, 3), (2, 4), (3, 2), (4, 1), (5, 1), (1, 2)]

It will loop through the list and creates a tuple with the item as its first element and its counts as second element.