matplotlib.pyplot.axhline(y=0, xmin=0, xmax=1, **kwargs)[source]

Add a horizontal line across the axis.

yfloat, default: 0

y position in data coordinates of the horizontal line.

xminfloat, default: 0

Should be between 0 and 1, 0 being the far left of the plot, 1 the far right of the plot.

xmaxfloat, default: 1

Should be between 0 and 1, 0 being the far left of the plot, 1 the far right of the plot.

Other Parameters:

Valid keyword arguments are Line2D properties, with the exception of 'transform':

Property Description
agg_filter a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array
alpha float or None
animated bool
antialiased or aa bool
clip_box Bbox
clip_on bool
clip_path Patch or (Path, Transform) or None
color or c color
contains unknown
dash_capstyle {'butt', 'round', 'projecting'}
dash_joinstyle {'miter', 'round', 'bevel'}
dashes sequence of floats (on/off ink in points) or (None, None)
data (2, N) array or two 1D arrays
drawstyle or ds {'default', 'steps', 'steps-pre', 'steps-mid', 'steps-post'}, default: 'default'
figure Figure
fillstyle {'full', 'left', 'right', 'bottom', 'top', 'none'}
gid str
in_layout bool
label object
linestyle or ls {'-', '--', '-.', ':', '', (offset, on-off-seq), ...}
linewidth or lw float
marker marker style string, Path or MarkerStyle
markeredgecolor or mec color
markeredgewidth or mew float
markerfacecolor or mfc color
markerfacecoloralt or mfcalt color
markersize or ms float
markevery None or int or (int, int) or slice or List[int] or float or (float, float) or List[bool]
path_effects AbstractPathEffect
picker unknown
pickradius float
rasterized bool or None
sketch_params (scale: float, length: float, randomness: float)
snap bool or None
solid_capstyle {'butt', 'round', 'projecting'}
solid_joinstyle {'miter', 'round', 'bevel'}
transform matplotlib.transforms.Transform
url str
visible bool
xdata 1D array
ydata 1D array
zorder float

See also

Add horizontal lines in data coordinates.
Add a horizontal span (rectangle) across the axis.
Add a line with an arbitrary slope.


  • draw a thick red hline at 'y' = 0 that spans the xrange:

    >>> axhline(linewidth=4, color='r')
  • draw a default hline at 'y' = 1 that spans the xrange:

    >>> axhline(y=1)
  • draw a default hline at 'y' = .5 that spans the middle half of the xrange:

    >>> axhline(y=.5, xmin=0.25, xmax=0.75)