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matplotlib-label-lines

library0.8.1pypypi✓ verified 90d ago

Label lines in matplotlib by adding text annotations near specified line segments. Version 0.8.1, supports Python >=3.9. Release cadence is low, no major updates in recent years.

data serialization

pip install matplotlib-label-lines

github ↗package ↗

INSTALL

IMPORT

SIG · MATPLOTLIB-LABEL-L

matplotlib-label-lines

datapythonv0.8.1

Install

7.7s avg

Import

2705ms

Disk

182MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v0.8.1 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 2.744s · 179MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 7.7s · import 2.666s · 171MB

182MB installed

● package 182MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

labelLines

✓ from labellines import labelLines

✗ import labelLines

Module name is 'labellines' (no spacing), function is labelLines.

labelLine

✓ from labellines import labelLine

✗ from labellines import label_lines

Function is camelCase, not snake_case.

Basic example: plot three lines and label them with automatic positioning.

import matplotlib.pyplot as plt import numpy as np from labellines import labelLines x = np.linspace(0, 1, 100) fig, ax = plt.subplots() for i in range(1, 4): ax.plot(x, x**i, label=f'$x^{i}$') labelLines(ax.get_lines()) plt.show()

Debug

Known issues

gotchalabelLines uses the line's label for text; if no label is set, it silently skips the line.

fix

Ensure every line you want labeled has a label string set via the 'label' parameter in plot.

affects: all

gotchalabelLines positions labels based on the data range; if x or y data is not sorted, label placement may be unexpected.

fix

Sort your data before plotting or use labelLine for manual control.

affects: all

deprecatedIn matplotlib 3.7+, get_lines() returns an immutable sequence; modifying the returned list is no longer possible.

fix

No change needed for labeling, but do not attempt to mutate ax.get_lines() directly.

affects: >=0.8.1

gotchaThe 'xvals' parameter expects x-coordinate values in data space; if you pass fractional axes coordinates, labels will be misplaced.

fix

Use data coordinates for xvals, or convert using ax.transData.transform().

affects: all

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'labellines'

Attempted import with wrong name (e.g., 'matplotlib_label_lines' or 'labellines' misspelled).

fix

Install via pip and use: from labellines import labelLines

ImportError: cannot import name 'labelLines' from 'labellines'

Older version of the library (before 0.6.0) used a different function name or the module is not installed correctly.

fix

Upgrade to latest version: pip install --upgrade matplotlib-label-lines

KeyError: 'label' when calling labelLines

One or more lines in the collection do not have a label set (label is empty or None).

fix

Set label for each line: plt.plot(x, y, label='my line') or pass lines with labels only.

Upgrade

Version history

0.8.1latest on PyPI · released Apr 25, 2025

Audit

Dependencies

matplotlibrequiredRequired for plotting

numpyrequiredUsed internally for coordinate handling

Agent activity

8 hits · last 30 days

node

Resources

githubhttps://github.com/cphyc/matplotlib-label-lines ↗

packagehttps://pypi.org/project/matplotlib-label-lines/ ↗