Python: most idiomatic way to convert None to empty string?

Question

What is the most idiomatic way to do the following?

def xstr(s):
    if s is None:
        return \'\'
    else:
        return s

s = xstr(a) + xstr(b)
         


        

Answer 1

If you know that the value will always either be a string or None:

xstr = lambda s: s or ""

print xstr("a") + xstr("b") # -> 'ab'
print xstr("a") + xstr(None) # -> 'a'
print xstr(None) + xstr("b") # -> 'b'
print xstr(None) + xstr(None) # -> ''