Something basic about lists and loops that I'm not getting here. I've got
a long list of dictionaries that looks like this:
lst = [{'placename': u'Stow, Lincolnshire', 'long-name': u'Stow,
Lincolnshire.', 'end': datetime.date(1216, 9, 28), 'start':
datetime.date(1216, 9, 26)},
{'placename': u'Lincoln, Lincolnshire', 'long-name': u'Lincoln,
Lincolnshire.', 'end': datetime.date(1216, 9, 30), 'start':
datetime.date(1216, 9, 28)},
{'placename': u'Lincoln, Lincolnshire', 'long-name': u'Lincoln,
Lincolnshire.', 'end': datetime.date(1216, 10, 2), 'start':
datetime.date(1216, 10, 1)},
{'placename': u'Grimsby, Lincolnshire', 'long-name': u'Grimsby,
Lincolnshire.', 'end': datetime.date(1216, 10, 4), 'start':
datetime.date(1216, 10, 3)},
{'placename': u'Louth, Lincolnshire', 'long-name': u'Louth,
Lincolnshire.', 'end': datetime.date(1216, 10, 4), 'start':
datetime.date(1216, 10, 4)}
]
I have a function that searches through them to find pairs of dictionaries
that satisfy certain criteria. When the nested loops find such a pair, I
need to merge them. So far so good. This works:
def events(data):
evts = []
for x in lst:
for y in lst:
if (x['placename'] == y['placename']) and (x['end'].month + 1 ==
y['start'].month) and (y['start'] - x['end'] == datetime.timedelta(1)):
evts.append({'placename': x['placename'], 'long-name':
x['long-name'], 'start': x['start'], 'end': y['end']})
evts.append(x)
return evts
for x in events(lst):
print x
But then I need to delete the two original dictionaries that I merged. If
I do del x, I get an error "local variable 'x' referenced before
assignment"
I've also tried decorating the processed dictionaries in the if loop thus:
x['processed'] = True
y['processed'] = True
Then when I call events() I get back the merged dict and the decorated
dicts:
{'placename': u'Lincoln, Lincolnshire', 'end': datetime.date(1216, 10, 2),
'start': datetime.date(1216, 9, 28), 'long-name': u'Lincoln,
Lincolnshire.'}
{'placename': u'Lincoln, Lincolnshire', 'processed': True, 'end':
datetime.date(1216, 9, 30), 'start': datetime.date(1216, 9, 28),
'long-name': u'Lincoln, Lincolnshire.'}
{'placename': u'Lincoln, Lincolnshire', 'processed': True, 'end':
datetime.date(1216, 10, 2), 'start': datetime.date(1216, 10, 1),
'long-name': u'Lincoln, Lincolnshire.'}
But if I try to call events() thus:
for x in events(lst):
if x['processed'] == True:
print x
I get a KeyError.
Could someone explain what's going on here?
Thanks,
Jon
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