Controlling contour label formatting in pyplot
<p>I'm making a plot where I have contours at <code>[2000, 4000, 6000, 8000]</code>.  The contours are labeled as 2000.000, 4000.000 etc.  I'd like to get rid of all those trailing zeros.  The best option I can find right now is here: <a href="http://matplotlib.org/examples/pylab_examples/contour_label_demo.html" rel="nofollow">http://matplotlib.org/examples/pylab_examples/contour_label_demo.html</a>, which suggests defining a new class for the labels which controls how they are displayed, and then using that class.  I've never seen such a convoluted option in python before.  Is there no more direct way?</p>

<p>Here is the code provided as an example of defining a class for the labels.</p>

<pre><code>import matplotlib
import numpy as np
import matplotlib.cm as cm
import matplotlib.mlab as mlab
import matplotlib.ticker as ticker
import matplotlib.pyplot as plt

matplotlib.rcParams['xtick.direction'] = 'out'
matplotlib.rcParams['ytick.direction'] = 'out'

##################################################
# Define our surface
##################################################
delta = 0.025
x = np.arange(-3.0, 3.0, delta)
y = np.arange(-2.0, 2.0, delta)
X, Y = np.meshgrid(x, y)
Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
# difference of Gaussians
Z = 10.0 * (Z2 - Z1)

##################################################
# Make contour labels using creative float classes
# Follows suggestion of Manuel Metz
##################################################
plt.figure()

# Basic contour plot
CS = plt.contour(X, Y, Z)


# Define a class that forces representation of float to look a certain way
# This remove trailing zero so '1.0' becomes '1'
class nf(float):
    def __repr__(self):
        str = '%.1f' % (self.__float__(),)
        if str[-1] == '0':
            return '%.0f' % self.__float__()
        else:
            return '%.1f' % self.__float__()

# Recast levels to new class
CS.levels = [nf(val) for val in CS.levels]

# Label levels with specially formatted floats
if plt.rcParams["text.usetex"]:
    fmt = r'%r \%%'
else:
    fmt = '%r %%'
plt.clabel(CS, CS.levels, inline=True, fmt=fmt, fontsize=10)
</code></pre>

<p>The <code>fmt</code> parameter can be either a classic format string or a callable that converts a scalar to a string.</p>

<p>If you don't have fancy requirements you could just pass <code>fmt='%d'</code> instead of a custom class.</p>

<p>For common formats you should be also able to resort to the default formatters in <code>matplotlib.ticker</code> before having to implement your own. </p>

python matplotlib