Matplotlib legend() Function |

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Matplotlib Reference Documentation

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The legend() function is used to add a legend to a chart, helping readers identify the meaning of each curve or dataset.

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Function Definition

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matplotlib.pyplot.legend(*args, **kwargs)\\nAxes.legend(*args, **kwargs)\\nFigure.legend(*args, **kwargs)\\n

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Common Parameters

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Parameter	Type	Description
loc	str or int	Legend location: 'best' (automatic), 'upper right', 'upper left', 'lower left', 'lower right', 'right', 'center left', 'center right', 'lower center', 'upper center', 'center', 'outside' (outside)
bbox_to_anchor	tuple	Legend anchor coordinates, used with loc for precise positioning. For example, (1.05, 1) places the legend in the upper-right corner outside the Axes.
ncol	int	Number of legend columns; default is 1. Multiple entries are displayed in multiple columns.
fontsize	int or str	Legend font size, e.g., 10, 'small', 'large'
frameon	bool	Whether to show the legend frame; default is True
shadow	bool	Whether to add a shadow effect
title	str	Legend title
facecolor	color	Legend background color
edgecolor	color	Legend frame color
fancybox	bool	Whether to use rounded frame corners; default is True
markerscale	float	Scaling factor for markers in the legend relative to the original markers
handlelength	float	Length of line handles in the legend

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The legend only displays Artists that have the label parameter set. A common practice is to directly specify label in plotting functions such as plot(), scatter(), bar(), and then call legend().

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Usage Examples

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Example 1: Basic Legend

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Examples

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import matplotlib.pyplot as plt\\nimport numpy as np\\n\\nx = np.linspace(0,10,100)\\n\\nfig, ax = plt.subplots(layout='constrained')\\n\\n# The label for each curve is automatically added to the legend\\n ax.plot(x, np.sin(x), label='sin(x)')\\n ax.plot(x, np.cos(x), label='cos(x)')\\n ax.plot(x, np.sin(x) * np.exp(-x/3), label='damped sin(x)')\\n\\nax.legend(loc='upper right')# Automatically collect all labels\\n ax.set_title('Basic Legend')\\n ax.set_xlabel('x')\\n ax.grid(True, alpha=0.3)\\n\\n plt.show()\\n

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Example 2: Legend Outside the Plot + Multiple Columns

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Examples

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import matplotlib.pyplot as plt\\nimport numpy as np\\n\\nx = np.linspace(0,10,100)\\n\\nfig, ax = plt.subplots(figsize=(8,4), layout='constrained')\\n\\n# Plot multiple curves\\nfor i in range(6):\\n ax.plot(x, np.sin(x + i * 0.5), label=f'sin(x + {i*0.5:.1f})')\\n\\n# Place the legend outside the Axes and display it in two columns\\n ax.legend(loc='upper left',\\n bbox_to_anchor=(1.02,1),# Outside upper right corner\\n ncol=2,# Display in two columns\\n title='Phase Shift',\\n frameon=True,\\n fancybox=True,\\n shadow=True)\\n\\nax.set_title('Legend Outside the Plot (ncol=2)')\\n ax.set_xlabel('x')\\n ax.grid(True, alpha=0.3)\\n\\n plt.show()\\n

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Example 3: Custom Legend Entries

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Examples

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import matplotlib.pyplot as plt\\nimport matplotlib.patches as mpatches\\nimport numpy as np\\n\\nx = np.linspace(0,10,100)\\n\\nfig, ax = plt.subplots(layout='constrained')\\n\\nax.plot(x, np.sin(x),'b-', linewidth=2)\\n ax.plot(x, np.cos(x),'r--', linewidth=2)\\n\\n# Manually specify legend entries (not associated with plot labels)\\n blue_line = mpatches.Patch(color='blue', label='Sine Wave')\\n red_line = mpatches.Patch(color='red', label='Cosine Wave')\\n\\nax.legend(handles=[blue_line, red_line],\\n loc='upper right',\\n fontsize=11)\\n\\nax.set_title('Custom Legend Handles')\\n ax.set_xlabel('x')\\n ax.grid(True, alpha=0.3)\\n\\n plt.show()\\n

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Example 4: Legend Location Quick Reference

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Examples

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import matplotlib.pyplot as plt\\n\\n# Show the positions corresponding to all loc codes\\n locations =[\\n'upper left','upper right','lower left','lower right',\\n'center left','center right','lower center','upper center',\\n'center'\\n]\\n\\nfig, axes = plt.subplots(3,3, figsize=(10,8),\\n layout='constrained')\\n\\n axes = axes.flatten()\\n\\nfor ax, loc in zip(axes, locations):\\n ax.plot([0,1],[0,1],'b-', label='Line A')\\n ax.plot([0,1],[1,0],'r--', label='Line B')\\n ax.legend(loc=loc, fontsize=8, title=f'loc="{loc}"')\\n ax.set_xticks([])\\n ax.set_yticks([])\\n\\nfig.suptitle('All legend() Locations', fontsize=14)\\n\\n plt.show()\\n

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Frequently Asked Questions

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Legend Not Showing?

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• Check whether the plotting functions have the label parameter set.
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• Ensure that the legend() function is called.
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• If certain Artists should not appear in the legend, set their label to an empty string or '_nolegend_'.
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How to Partially Modify Line Styles in the Legend?

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Retrieve the line objects in the legend via legend.get_lines() and modify their properties, or use the handler_map parameter.

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Matplotlib Reference Documentation