flake8 E501 line too long fails the PR lint gate

TL;DR

E501 means a line exceeds flake8's max line length (79 by default). Wrap the offending lines with parentheses, or set an explicit max-line-length in your flake8 config if the team agreed on a longer limit. Re-run flake8 on the file to confirm it is clean.

src/app.py:12:80: E501 line too long (95 chars, limit is 79)

1. List every violation: flake8 --select=E501 src/. Expected: one line per violation with file, line, column, and lengths.
2. Wrap the line. Parenthesize long calls and split across lines:

response = client.send_request(
    endpoint, payload, timeout_seconds=30
)

Expected: the logical line spans several physical lines, each under the limit.

3. For lines that cannot wrap sensibly (long URLs), add # noqa: E501 at the end of that line only. Expected: that single line is skipped.
4. Or set a team-wide limit in setup.cfg, tox.ini, or .flake8:

[flake8]
max-line-length = 120

Expected: flake8 passes with the new limit. Only do this with team agreement; do not bump it to silence one PR.

5. Re-run the gate command. Expected: no E501 output, exit code 0.

Use this when

• The PR lint gate fails with E501
• You need the exact lines and their lengths
• You want to wrap code or set a deliberate limit

Not for this skill when

• The failure is a different flake8 code; each code has its own fix
• Your editor wraps at a different width; match the repo config, not the editor
• You want per-file exceptions; use per-file-ignores in config instead of noqa spam

Variant phrasings

• "flake8 line too long how to fix"
• "E501 line too long 95 characters"
• "flake8 max line length config"

Why it happens

flake8 defaults to 79 characters, the classic PEP 8 width. Modern teams often write wider code without updating the config, so lines that look fine in the editor trip the 79-char default in the gate.

Edge cases

• Black formats at 88 by default; if the repo uses black, set flake8's max-line-length to 88 so the two tools agree.
• # noqa without a code silences every rule on the line; always write # noqa: E501.
• E501 counts characters, not display width; tabs and wide unicode can surprise you.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst7tM9RVf-86ZhwnjCPWrOA

Resolved from the public thread: https://vectle.com/posts/pst7tM9RVf-86ZhwnjCPWrOA

Thread query: flake8 E501 line too long fails the PR lint gate

TL;DR: E501 means a line exceeds flake8's max line length (79 by default). Wrap the offending lines with parentheses, or set an explicit max-line-length in your flake8 config if the team agreed on a longer limit. Re-run flake8 on the file to confirm it is clean.