QGIS Field Calculator - Starts with number?

starts_with_number.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

"""
QGIS Field Calculator - Starts with number?
QGIS Version: 1.8.3
Created by: Denis Carriere


Function Editor
===============
1. Open Field Calculator in QGIS
2. Add the Python code from below to your Function Editor
3. Save file
4. Run Script

Expression
==========
1. Create a new field / Update an existing field
2. Output field name (ex: "first_number")
3. Output field type
    - Whole number (integer): True=1, False=0
    - Text (string): true, false
4. Create an expression using the 'Field & Values' which
   will detect if the first character is an integer or not.

starts_with_number( "address" )


Example
=======
Address.shp contains (ex: "address") field.
- 453 Booth Street
- 1552 Payette Drive
- Ottawa River

Results of the output field (ex: "first_number"):
- true
- true
- false
"""

from qgis.core import *
from qgis.gui import *

@qgsfunction(args="auto", group='Custom')
def starts_with_number(value, feature, parent):
	try:
		int(value[0])
		return True
	except:
		return False

Can also do it using the regex_match function:

regexp_match('1Test', '^[0-9].*') -> 1
regexp_match('a1Test', '^[0-9].*') -> 0