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line-too-long (E501)

Derived from the pycodestyle linter.

What it does

Checks for lines that exceed the specified maximum character length.

Why is this bad?

Overlong lines can hurt readability. PEP 8, for example, recommends limiting lines to 79 characters. By default, this rule enforces a limit of 88 characters for compatibility with Black and the Ruff formatter, though that limit is configurable via the line-length setting.

In the interest of pragmatism, this rule makes a few exceptions when determining whether a line is overlong. Namely, it:

  1. Ignores lines that consist of a single "word" (i.e., without any whitespace between its characters).
  2. Ignores lines that end with a URL, as long as the URL starts before the line-length threshold.
  3. Ignores line that end with a pragma comment (e.g., # type: ignore or # noqa), as long as the pragma comment starts before the line-length threshold. That is, a line will not be flagged as overlong if a pragma comment causes it to exceed the line length. (This behavior aligns with that of the Ruff formatter.)
  4. Ignores SPDX license identifiers and copyright notices (e.g., # SPDX-License-Identifier: MIT), which are machine-readable and should not wrap over multiple lines.

If lint.pycodestyle.ignore-overlong-task-comments is true, this rule will also ignore comments that start with any of the specified lint.task-tags (e.g., # TODO:).

Example

my_function(param1, param2, param3, param4, param5, param6, param7, param8, param9, param10)

Use instead:

my_function(
    param1, param2, param3, param4, param5,
    param6, param7, param8, param9, param10
)

Error suppression

Hint: when suppressing E501 errors within multi-line strings (like docstrings), the noqa directive should come at the end of the string (after the closing triple quote), and will apply to the entire string, like so:

"""Lorem ipsum dolor sit amet.

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor.
"""  # noqa: E501

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