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    update  I m incorporating Tryptich s suggestion to use str s   which makes this routine work for other types besides strings   I m awfully impressed by Vinay Sajip s lambda suggestion  but I want to keep my code relatively simple   def xstr s       if s is None          return        else          return str s

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A neat one-liner to do this building on some of the other answers   s    lambda v  v or     a     lambda v  v or     b    or even just   s    a or        b or

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Functional way  one-liner   xstr   lambda s     if s is None else s

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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

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return s or    will work just fine for your stated problem

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def xstr s       return s if s else     s     s s     xstr a   xstr b

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Use F string if you are using python v3 7  xstr   F  s

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Variation on the above if you need to be compatible with Python 2 4  xstr   lambda s  s is not None and s or

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We can always avoid type casting in scenarios explained below   customer    John  name   str customer  if name is None    print  Name is blank  else      print  Customer name       name   In the example above in case variable customer s value is None the it further gets casting while getting assigned to  name   The comparison in  if  clause will always fail    customer    John    even though its None still it will work properly  name   customer if name is None    print  Name is blank  else      print  Customer name       str name    Above example will work properly  Such scenarios are very common when values are being fetched from URL  JSON or XML or even values need further type casting for any manipulation

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If it is about formatting strings  you can do the following   from string import Formatter  class NoneAsEmptyFormatter Formatter       def get value self  key  args  kwargs           v   super   get value key  args  kwargs          return    if v is None else v  fmt   NoneAsEmptyFormatter   s   fmt format         a  b

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def xstr s       return    if s is None else str s

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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

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If you know that the value will always either be a string or None   xstr   lambda s  s or     print xstr  a     xstr  b     - gt   ab  print xstr  a     xstr None    - gt   a  print xstr None    xstr  b     - gt   b  print xstr None    xstr None    - gt

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Probably the shortest would be  str s or      Because None is False  and  x or y  returns y if x is false  See Boolean Operators for a detailed explanation  It s short  but not very explicit

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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

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def xstr s      return s or

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def xstr s       return  None     get s  s

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