import fnmatch
from pathlib import Path

directory = "directory/"

for dirpath, dirs, files in os.walk(directory):
    for filename in fnmatch.filter(files, '*.html'):
        with open(os.path.join(dirpath, filename)) as f:
            html = f.read()
            if 'apples and oranges' in html:
                with open('output.csv', 'w') as f:
                    writer = csv.writer(f)
                    lines = [[html]]
                    for l in lines:
                        writer.writerow(l)