Text file with one very long line

Handle it in code

Each snippet below was run against this exact file with Python 3.14.4 and Node 24.15.0 when this page was built, and the output shown is what it printed.

Python

Read the bytes, not text mode, so the line endings survive to be counted. Invisible format characters (category Cf: zero-width spaces, direction overrides, the BOM) are the ones that make two identical-looking strings compare unequal.

import unicodedata

with open("very-long-single-line.txt", "rb") as f:
    data = f.read()
crlf = data.count(b"\r\n")
lf, cr = data.count(b"\n") - crlf, data.count(b"\r") - crlf
print(f"line endings: {crlf} CRLF, {lf} LF, {cr} bare CR")
print("ends with a newline" if data.endswith(b"\n") else "no newline at the end of the file")
text = data.decode("utf-8")
print(f"longest line: {max(map(len, text.splitlines()), default=0):,} characters")
hidden = sorted({f"U+{ord(c):04X} {unicodedata.name(c, '?')}" for c in text if unicodedata.category(c) == "Cf"})
print("invisible characters:", ", ".join(hidden) if hidden else "none")

Run against this file, it prints: line endings: 0 CRLF, 0 LF, 0 bare CR no newline at the end of the file longest line: 1,024,000 characters invisible characters: none