If the value is None, I'd like to change it to "" (empty string).
I start off like this, but I forget:
for k, v in mydict.items():
if v is None:
... right?
views:
368answers:
3
+6
A:
for k, v in mydict.iteritems():
if v is None:
mydict[k] = ''
In a more general case, e.g. if you were adding or removing keys, it might not be safe to change the structure of the container you're looping on -- so using items to loop on an independent list copy thereof might be prudent -- but assigning a different value at a given existing index does not incur any problem, so, in Python 2.any, it's better to use iteritems.
Alex Martelli
2010-02-23 01:21:31
perhaps s/index/key/
John Machin
2010-02-23 01:58:39
@John, it applies to _any_ built-in **container** -- just as much to a list as to a dict -- and I think "index" is a more generic term than "key".
Alex Martelli
2010-02-23 02:10:27
A:
Comprehensions are usually faster, and this has the advantage of not editing mydict during the iteration
mydict = dict([(k, v if v else "") for k,v in mydict.items()])
mountainswhim
2010-02-23 01:27:43
If you are using `.items()` it doesn't matter (for python2) if you modify `mydict` as the list that `.items()` returns will not change even if you add/remove keys of `mydict`
gnibbler
2010-02-23 01:30:47
Changing only values in a dict is never a problem; grief is caused by adding/deleting KEYS while iterating over the dict. Comprehensions are faster than WHAT? Really fast: copying the whole dict when there's one or two Nones to change. Speaking of Nones, you should have `if v is not None` instead of `if v` (re-read the question). Overall summary: -1
John Machin
2010-02-23 02:06:27