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

Use short circuit evaluation:

s = a or '' + b or ''

Since + is not a very good operation on strings, better use format strings:

s = "%s%s" % (a or '', b or '')

Answer 2

Use F string if you are using python v3.7

xstr = F"{s}"

Answer 3

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) # -> ''

Answer 4

Variation on the above if you need to be compatible with Python 2.4

xstr = lambda s: s is not None and s or ''

Answer 5

If you actually want your function to behave like the str() built-in, but return an empty string when the argument is None, do this:

def xstr(s):
    if s is None:
        return ''
    return str(s)

Answer 6

I use max function:

max(None, '')  #Returns blank
max("Hello",'') #Returns Hello

Works like a charm ;) Just put your string in the first parameter of the function.