Question

Is there a standard library function or more pythonic way to do this ?

def itemize(i):
    if type(i) is list:
        return i
    return [i]

Context:

Useful in db (nosql style) migrations from single value to a list

doc = <get doc from db>
for i in itemize(doc.var1):
    #blah

or

doc.var1 = itemize(doc.var1)

Answer 1

Usually, enforcing this sort of thing is a bad idea. In many cases, the most pythonic thing you can do is check if your item is a sequence:

import collections
def to_sequence(item):
    return item if isinstance(item,collections.Sequence) else [item]

One instance where this passes something that you may not want to pass is with strings … strings are sequences, so to_sequence('foo') will return 'foo', not ['foo'] — but it’s unlikely that you want it to be ['f','o','o'] either … so you might need to special case for that if it’s desired.

One simple fix for that would be (for python2.x):

import collections
def to_sequence(item):
    return item if isinstance(item,collections.Sequence) and hasattr(item,'__iter__') else [item]

But again, usually the “pythonic” thing to do is to defer this sort of checking and try to use the object in some context — if it fails, then you can do something to react.