Get number from string in python

import sys
import re

a = sys.argv[1]
print(a)
m1 = re.search("[^0-9\.]", a) # str
m2 = re.search("[0-9\.]", a)  # num
if m1 and m2:
  print("m1.start(),m2.start():",m1.start(),m2.start())
  if m1.start() > m2.start():
    ret = a[:m1.start()]
  else:
    ret = a[m2.start():]
    print("ret:",ret)
    m3 = re.search("[^0-9\.]", ret)
    if m3:
      ret = ret[:m3.start()]
elif m1:
  # only str
  ret = ""
elif m2:
  # only num
  ret = a
print("ret:",ret)