You can use re
module for the task:
style="fill: rgb(0, 0, 0); fill-opacity: 1; font-family: ProjectStocksFont; font-size: 70px; font-weight: normal; font-style: normal; text-decoration: none;"
import re
print( re.search(r'font-size:\s*(\d+)', style)[1] )
Prints:
70
3
solved Python get info from long complicated string