[Python] Qn: Nested dictionary cleanup

Colin> for key1 in dict1.keys():
Colin> for key2 in dict1[key1]:
Colin> if dict1[key1][key2] == None:
Colin> del dict1[key1][key2]

Should be

for key1 in dict1.keys():
for key2 in dict1[key1].keys():
if dict1[key1][key2] == None:
del dict1[key1][key2]

Note that the inner for loop explicitly calls .keys(). That creates an
explicit list. You loop over that instead of an iterator. Why did you
choose to call dict1.keys() but not dict1[key1].keys()?

Skip

here you step through an iterator. If you change this to
for key2 in dict1[key1].keys():

and assuming I've guessed appropriately, you might get what you're looking
for.
Emile van Sebille
emile at fenx.com

OOPS!

Coding slip I'm afraid, sorry. I was thinking that the
code was failing because keys() were being evaluated
dynamically. I then tried to think how to queue the
deletes to be done after the loop but could not
figure out how to do this.

Colin

"Colin Brown" <cbrown at metservice.com> wrote in message
news:3fa6c327$1 at news.iconz.co.nz...

In addition to Emile van Sebille's fix, the following tries to avoid
dictionary lookups:

# dict1 is not changed so we need not copy the values
for innerdict in dict1.itervalues():
# innerdict is changed so let's make a copy of the items
for key, value in innerdict.items():
if value is None:
del innerdict[key]


Peter