On Fri, Jan 2, 2009 at 8:17 AM, Norman Khine <nor...@khine.net> wrote:
> Hello,
> I have this list
>
>>>> currencies = [{'sign': '\xe2\x82\xac', 'id': 'EUR', 'is_selected':
>>>> False, 'title': 'EURO'}, {'sign': '\xc2\xa3', 'id': 'GBP', 'is_selected':
>>>> True, 'title': 'Pound'}, {'sign': '$', 'id': 'USD', 'is_selected': False,
>>>> 'title': 'Dollar'}]
>
> What is the simplest way to extract the dictionary that has key
> 'is_selected'== True?
A list comprehension can extract a list of all dicts with the desired key:
In [2]: [ currency for currency in currencies if currency['is_selected'] ]
Out[2]: [{'id': 'GBP', 'is_selected': True, 'sign': '\xc2\xa3',
'title': 'Pound'}]
A generator expression lets you pick out just the first one without
iterating the whole list. This will raise StopIteration if there is no
selected item:
In [3]: ( currency for currency in currencies if
currency['is_selected'] ).next()
Out[3]: {'id': 'GBP', 'is_selected': True, 'sign': '\xc2\xa3', 'title': 'Pound'}
Of course a for loop works. You can use the else clause to handle the
case of no selection:
for currency in currencies:
if currency['is_selected']:
# Do something with currency
print currency
break
else: # this matches the indentation of 'for', it is not an 'elif'
# Handle 'not found' case
print 'No currency selected'
Kent
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