(Hacky) recursive grep in Python

string_search.py

#!/usr/bin/env python3
import os

user_input = input('What is the name of your directory?\n')
searchstring = input('What string are you trying to find?\n')

def recr(dir):
    for fname in os.listdir(dir):
        rel_fname = dir + os.sep + fname
        if os.path.isfile(rel_fname):
            file_search(rel_fname, searchstring)
        elif os.path.isdir(rel_fname):
            recr(rel_fname)

def file_search(fname, searchstring):
    # Full path
    try:
        f = open(fname, 'r')
        if searchstring in f.read():
            print('Found string in file: %s' % fname)
        f.close()
    except Exception:
        pass

recr(user_input)
print('Search complete')