how to remove all letters in a string python regex code example

Example: strip characters from string python regex

syntax
re.sub(pattern, repl, string, max=0)
#!/usr/bin/python
import re

phone = "2004-959-559 # This is Phone Number"

# Delete Python-style comments
num = re.sub(r'#.*$', "", phone)
print "Phone Num : ", num
#output Phone Num :  2004-959-559

# Remove anything other than digits
num = re.sub(r'\D', "", phone)    
print "Phone Num : ", num
#output Phone Num :  2004959559