function to remove character from string in python code example

Example 1: python remove letters from string

string = "abc123"
# Method 1
''.join(char for char in string if char.isdigit())

#Method 2
import re
re.sub("[^0-9]", "", string)

Example 2: how to remove letters from string

public extractLetters(String str){
	String result="";
	for(int i= 0; i< str.length; i++){
	    if(Character.isLetter(str.charAt(i))){
	    result+=str.charAt(i);
	  	}
	}