Runs GNU Diff and [diffr](https://github.com/mookid/diffr) to compare strings without tempfiles. UNIX only.

diffr-python-strings.py

import os
import threading
import subprocess

before = ""
after = ""

before_read_fd, before_write_fd = os.pipe()
after_read_fd, after_write_fd = os.pipe()
diff_proc = subprocess.Popen(
    [
        "diff",
        "-u",
        "--color=always",
        f"/dev/fd/{before_read_fd}",
        f"/dev/fd/{after_read_fd}",
    ],
    pass_fds=[before_read_fd, after_read_fd],
    stdout=subprocess.PIPE,
    stderr=subprocess.STDOUT,
)
before_write_thread = threading.Thread(
    target=os.write, args=(before_write_fd, before.encode())
)
after_write_thread = threading.Thread(
    target=os.write, args=(after_write_fd, after.encode())
)
before_write_thread.start()
after_write_thread.start()
before_write_thread.join()
after_write_thread.join()
os.close(before_write_fd)
os.close(after_write_fd)
diff_output, _ = diff_proc.communicate()
diffr_proc = subprocess.Popen(
    "diffr", stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT
)
diffr_output, _ = diffr_proc.communicate(input=diff_output)
print(diffr_output.decode())