Using Python Function in Field Calculator to find numbers

Question

Disclaimer, I am terrible at writing my own functions especially in the field calculator. I have an address field (Address) with records that are missing street numbers. I would like to find these records, skip over them, and populate a field (Number) with the first element of the records that do have a street number. I would like to do this in the field calculator if possible (ArcMap 10.2.2, Basic).

Here's what I got so far:

def findNumbers(Address):
  if Address.split(" ")[0].isalpha():
    pass
  elif int(Address.split(" ")[0]) >= 0:
    Number = Address.split[0]

Number = 
def findNumbers(!Number!)

Answer 1

Regular expressions are nice for extraction.

import re
def extract(s):        
    num = re.search('^\d+', s)  # find all leading digits
    if num is None:
        return None
    else:
        return int(num.group())

Answer 2

This question is most certainly a duplicate, but anyway I'd use:

def getNumber(aString):
 aList=aString.split();n=len(aList)
 if n>1:
  try: aNumber= int(aList[0]);return aNumber
  except: return -1
 else: return -1
#-----------------------
getNumber(!address!)

providing there are now houses like 23B, i.e. non-numeric suffix is absent