how to delete the [] from string python code example

Example 1: python remove string from string

s = 'ab12abc34ba'
print(s.replace('ab', ''))

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);
	  	}
	}