prices.py

from lxml import html
import requests
import numpy

page = requests.get('https://cloud.google.com/compute/pricing')
tree = html.fromstring(page.content)

lowest = tree.xpath('//table/tbody/tr/th[text()="Preemptible price"]/../../tr/td[5]/text()')[:18]

lowest_preempt = tree.xpath('//table/tbody/tr/th[text()="Preemptible price"]/../../tr/td[8]/text()')[:18]

lwst = [ float(x[1:]) for x in lowest ]
lwst_pr = [ float(x[1:]) for x in lowest_preempt ]

v = [ 100 * lwst_pr[i] / lwst[i] for i in range(0,len(lwst)) ]

# considering all cases
print "Considering all cases: "
print "Mean:",numpy.mean(v)
print "Std:",numpy.std(v)

# excluding shared-core machines
v = v[0:5] + v[8:]

print "Excluding shared-core machines"
print "Mean:",numpy.mean(v)
print "Std:",numpy.std(v)