CODEWITHSUNDEEP
pythonpython-2.7
Chris
Chris

Reputation: 28064

Unpack a tuple with a single element or return None if tuple is None

Using python 2.7, I have the following code:

if result != None:
    (data,) = result
    return data

return None

The result variable is returned from a sqlite3 query that returns only one value. If the query returns a result, I want to unpack and return the data, otherwise I want to return None. The code above seems overly verbose and not at all pythonic. Is there a better way?

Upvotes: 3

Views: 9389

Answers (5)

Pierre GM
Pierre GM

Reputation: 20339

Apart from the ; that you left and the fact that result != None should be replaced by result is not None, I have no issues with your code.

It's simple, quite understandable, and won't silently fail you if one of these days your request returns 2 elements or more: it will raise an exception instead of silently returning the first element, like all the solutions so far.

Upvotes: 0

Martijn Pieters
Martijn Pieters

Reputation: 1123420

You could use a if else condition:

return result[0] if result is not None else None

or simplify this down to:

return result[0] if result else None

if you don't care about result possibly being some other false-y value such as an empty tuple and such.

Upvotes: 10

mgilson
mgilson

Reputation: 310049

I suppose no answer is complete without try/except:

try:
   return result[0]
except TypeError,IndexError:
   return None

Upvotes: 1

pr0gg3d
pr0gg3d

Reputation: 977

A way could be:

if result is not None:
    return result[0]
return None

There is also a more compact way to do this:

return (result or [None])[0]

but the first is more clear.

Please avoid using semicolon at the end (is not C code), and reading python documentation helps you. It's a well-spent time.

Upvotes: 2

vartec
vartec

Reputation: 134631

Assuming that you'll only get either non-empty tuple or None, the simplest way:

return result and result[0]

Upvotes: 4

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