Format nicely printed labels based on pi for matplotlib x-axis

pi_format.py

def format_frac(fr):
    '''Convert a/b to latex'''
    sp = str(fr).split('/')
    if len(sp) == 1:
        return sp[0]
    else:
        return r'$\frac{%s}{%s}$' % tuple(sp)
        
frac_size = 4
step = fractions.Fraction(1, frac_size)
ax.set_xticks([np.pi * j * step for j in range(2 * frac_size + 1)])
ax.set_xticklabels([format_frac(j * step) + '$\pi$' for j in range(2 * frac_size + 1)])