I am trying to create a neat legend in Pyplot. So far I have this:

    fig = plt.figure()
    ax = plt.gca()

    marker_size = [20.0, 40.0, 60.0, 100.0, 150.0]                              
    marker_color = ['black', 'red', 'pink', 'white', 'yellow']                  
                                                                                
    ranges = [0.0, 1.5, 20.0, 60.0, 500.0]                                      
                                                                                
    marker_edge_thickness = 1.2                                                 
    s = [(m ** 2) / 100.0 for m in marker_size]                                 
    scatter_kwargs = {'edgecolors' : 'k', 'linewidths' : marker_edge_thickness} 
                                                                                
    for i in range(len(marker_size)):                                           
                                                                                
        if i == (len(marker_size) - 1):                                         
                                                                                
            label_str = '{:>5.1f} $\leq$ H$_2$'.format(ranges[i])               
                                                                                
        else:                                                                   
                                                                                
            label_str = '{:>5.1f} $\leq$ H$_2$ < {:>5.1f}'.format(ranges[i], ranges[i   1]) 
                                                                                
        ax.scatter([], [], s = s[i], c = marker_color[i],                       
                label = label_str, **scatter_kwargs)                            
                                                                                
    #ax.legend(prop={'family': 'monospace'})                                    
    ax.legend()
                                                                 
    plt.show()

It is ok but the symbols don't align properly between the rows. I would like to align the rows at multiple points, with alignment on the decimal points, the less-than and greater-than symbols, and the H2. I could use a monotype font (as per this answer:

CodePudding user response：

This uses monospace type, but at least uses the appropriate font for the subscript of H

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = plt.gca()

marker_size = [20.0, 40.0, 60.0, 100.0, 150.0]                              
marker_color = ['black', 'red', 'pink', 'white', 'yellow']                  

ranges = [0.0, 1.5, 20.0, 60.0, 500.0]             
num_digits = [1,1,2,2,3]

marker_edge_thickness = 1.2                                                 
s = [(m ** 2) / 100.0 for m in marker_size]                                 
scatter_kwargs = {'edgecolors' : 'k', 'linewidths' : marker_edge_thickness} 

for i in range(len(marker_size)):                                           
    if i == (len(marker_size) - 1):                                         
        label_str = '{:.1f}$\leq \mathregular{}$'.format(ranges[i],r'{\ H_2\ }')               
    else:                   
        label_str = '{:>5.1f}$\leq \mathregular{}<${:>5.1f}'.format(ranges[i], r'{\ H_2\ }',ranges[i   1])
    ax.scatter([], [], s = s[i], c = marker_color[i],                       
            label = label_str, **scatter_kwargs)                            

ax.legend(prop={'family': 'monospace'})  

Result: