Partial coloring of text in matplotlib

Question

Is there a way in matplotlib to partially specify the color of a string?

Example:

plt.ylabel("Today is cloudy.")

How can I show "today" as red, "is" as green and "cloudy." as blue?

Answer 1

I only know how to do this non-interactively, and even then only with the 'PS' backend.

To do this, I would use Latex to format the text. Then I would include the 'color' package, and set your colors as you wish.

Here is an example of doing this:

import matplotlib
matplotlib.use('ps')
from matplotlib import rc

rc('text',usetex=True)
rc('text.latex', preamble='\usepackage{color}')
import matplotlib.pyplot as plt

plt.figure()
plt.ylabel(r'\textcolor{red}{Today} '+
           r'\textcolor{green}{is} '+
           r'\textcolor{blue}{cloudy.}')
plt.savefig('test.ps')

This results in (converted from ps to png using ImageMagick, so I could post it here):

Answer 2

Here's the interactive version. Edit: Fixed bug producing extra spaces in Matplotlib 3.

import matplotlib.pyplot as plt
from matplotlib import transforms

def rainbow_text(x,y,ls,lc,**kw):
    """
    Take a list of strings ``ls`` and colors ``lc`` and place them next to each
    other, with text ls[i] being shown in color lc[i].

    This example shows how to do both vertical and horizontal text, and will
    pass all keyword arguments to plt.text, so you can set the font size,
    family, etc.
    """
    t = plt.gca().transData
    fig = plt.gcf()
    plt.show()

    #horizontal version
    for s,c in zip(ls,lc):
        text = plt.text(x,y,s+" ",color=c, transform=t, **kw)
        text.draw(fig.canvas.get_renderer())
        ex = text.get_window_extent()
        t = transforms.offset_copy(text._transform, x=ex.width, units='dots')

    #vertical version
    for s,c in zip(ls,lc):
        text = plt.text(x,y,s+" ",color=c, transform=t,
                rotation=90,va='bottom',ha='center',**kw)
        text.draw(fig.canvas.get_renderer())
        ex = text.get_window_extent()
        t = transforms.offset_copy(text._transform, y=ex.height, units='dots')


plt.figure()
rainbow_text(0.05,0.05,"all unicorns poop rainbows ! ! !".split(), 
        ['red', 'orange', 'brown', 'green', 'blue', 'purple', 'black'],
        size=20)

Answer 3

Extending Yann's answer, LaTeX coloring now also works with PDF export:

import matplotlib
from matplotlib.backends.backend_pgf import FigureCanvasPgf
matplotlib.backend_bases.register_backend('pdf', FigureCanvasPgf)

import matplotlib.pyplot as plt

pgf_with_latex = {
    "text.usetex": True,            # use LaTeX to write all text
    "pgf.rcfonts": False,           # Ignore Matplotlibrc
    "pgf.preamble": [
        r'\usepackage{color}'     # xcolor for colours
    ]
}
matplotlib.rcParams.update(pgf_with_latex)

plt.figure()
plt.ylabel(r'\textcolor{red}{Today} '+
           r'\textcolor{green}{is} '+
           r'\textcolor{blue}{cloudy.}')
plt.savefig("test.pdf")

Note that this python script sometimes fails with Undefined control sequence errors in the first attempt. Running it again is then successful.