AttributeError: 'list' object has no attribute 'lower'

[Roy Smith]

In article <43a68990-d6cf-4362-8c47-b13ce780b068 at googlegroups.com>,
 Token Type <typetoken at gmail.com> wrote:

> Thanks very much for all of your tips. Take noun as an example. First, I need 
> find all the lemma_names in all the synsets whose pos is 'n'. Second, for 
> each lemma_name, I will check all their sense number. 
> 
> 1)  Surely,we can know the number of synset whose pos is noun by 
> >>> len([synset for synset in wn.all_synsets('n')])
> 82115
> 
> However, confusingly it is unsuccessful to get a list of lemma names of these 
> synsets by 
> >>> lemma_list = [synset.lemma_names for synset in wn.all_synsets('n')]
> >>> lemma_list[:20]
> [['entity'], ['physical_entity'], ['abstraction', 'abstract_entity'], 
> ['thing'], ['object', 'physical_object'], ['whole', 'unit'], ['congener'], 
> ['living_thing', 'animate_thing'], ['organism', 'being'], ['benthos'], 
> ['dwarf'], ['heterotroph'], ['parent'], ['life'], ['biont'], ['cell'], 
> ['causal_agent', 'cause', 'causal_agency'], ['person', 'individual', 
> 'someone', 'somebody', 'mortal', 'soul'], ['animal', 'animate_being', 
> 'beast', 'brute', 'creature', 'fauna'], ['plant', 'flora', 'plant_life']]
> >>> type(lemma_list)
> <type 'list'>
> 


> Though the lemma_list is a list in the above codes, it contains so many 
> unnecessary [ and ]. How come it is like this? But what we desire and expect 
> is a list without this brackets. Confused, I am really curious to know why.

It looks like synset.lemma_names gets you a list.  And then you're 
taking all those lists and forming them into a list of lists:

>>> lemma_list = [synset.lemma_names for synset in wn.all_synsets('n')]

I think what you want to study is the difference between list.append() 
and list.extend().  When you use the list builder syntax, you're 
essentially writing a loop which does append operations.  The above is 
the same as if you wrote:

lemma_list = list()
for synset in wn.all_synsets('n'):
    lemma_list.append(synset.lemma_names)

and I think what you're looking for is:

lemma_list = list()
for synset in wn.all_synsets('n'):
    lemma_list.extend(synset.lemma_names)