csv ... ungetestet

from collections import defaultdict


names = {
    "wall_top": "Wall_top_position.csv",
    "wall_bot": "Wall_bot_position.csv",
    "membrane_top": "Membrane_top.csv",
    "membrane_bot": "Membrane_bot.csv",
}

results = defaultdict(list)


for name, file in names.items():
    with open(file) as fd:
        reader = csv.reader(fd)
        for row in reader:
            results[name].append(row[5:7])