from urllib.request import urlretrieve
if input('Refresh local copy of SOI data from ftp.bom.gov.au/..?\n'
         'Empty input for NO, anything else for YES '
        ) > '':
    print('Loading...')
    urlretrieve('ftp://ftp.bom.gov.au/anon/home/ncc/www/sco/soi/soiplaintext.html',
                'soiplaintext.html')
data = []
with open('soiplaintext.html', 'r') as f:
    for line in f: # until table header (the line after '"`UNIQ--pre-00000001-QINU`"'
data = [float(_) for _ in data]
import numpy as np
x = 1876. + 1/24. + np.linspace(0., len(data)/12, len(data), endpoint=False)
n = 7
n2 = n//2
kernel = np.sin(np.pi*np.linspace(1/(n+1), 1., n, endpoint=False))
kernel /= np.sum(kernel)
av = np.convolve(data, kernel, mode='valid')
import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
plt.rcParams['svg.fonttype'] = 'none' # text as text, not curves
fig, ax = plt.subplots(1,1)
fig.set_size_inches(13, 4)
ax.fill_between(x[n2:-n2], av, 7., where= av > 7., facecolor='blue', interpolate=True)
ax.fill_between(x[n2:-n2], av,-7., where= av <-7., facecolor='red',  interpolate=True)
ax.plot(x[n2:-n2], av, 'k-', linewidth=0.4)
ax.plot(x, data, 'ko', markerfacecolor='#00000040', markeredgecolor='#00000000', markersize=3)
ax.set_xlim(x[0]-2., x[-1]+2.)
ax.set_ylim(-43., 40.)
ax.xaxis.set_major_locator(MultipleLocator(10.))
fig.tight_layout()
fig.text(.91,.88, 'La-Niña', color='blue', fontname='Verdana', fontsize=15)
fig.text(.91,.12, 'El-Niño', color='red',  fontname='Verdana', fontsize=15)
fig.savefig('SOI.svg', format='svg')
fig.show()
from re import sub
svg = open('SOI.svg', 'r').read() # In the file ...
svg = sub(r'[0-9]+\.[0-9]+', lambda x: str(round(float(x.group()), 1)), svg) # round to .1f,
STYLE = ' style="fill-opacity: 0.3; stroke: #000000; stroke-opacity: 0"'
rest = svg.split(STYLE)                                                   # draw the style info
rest[0] = sub('z\n" style="', 'z\n" style="fill-opacity: 0.3; ', rest[0]) # into the g element,
symbol = rest[1].split('"')[1][1:]    # identify the symbol name for the marker
svg = sub(symbol, 'o', ''.join(rest)) # and shorten it to "o",
svg = sub(' *<use x', '<use x', svg) # and finally unindent the most frequent lines.
open('SOI.svg', 'w').write(svg)