Get list out of other list

Question

For some reason I end up with having a "list within a list" which does not really make sense to me:

I got a variable which contains the following output:

>>> print(combined_result)
>>> [[('id1', 'titel1'), ('id2', 'titel2'), ('id3', 'titel3'), ('id3', 'titel4')]]

which is generated by the following code:

combined_result = []
def executequery(cursor):
        cursor.execute("SELECT id, title FROM database")
        records = cursor.fetchall()
        result = records
        combined_result.append(result)
        return

To actually get the first element of that combined list I call it with:

>>> print(combined_result[0][1])
>>> ('id1', 'titel1')

I am wondering whether this is the right way to do it? Or should I modify my code? It is a bit weird right to have a list within a list in my situation?

i suggest you use ORM like peewee. – Zaaferani Apr 21 '15 at 13:45 — Zaaferani, Apr 21 '15 at 13:45

score 1 · Answer 1 · answered Apr 21 '15 at 13:46

1

Just after the function add this

>>> combined_result=combined_result[0]

Output

>>> combined_result
[('id1', 'titel1'), ('id2', 'titel2'), ('id3', 'titel3'), ('id3', 'titel4')]

answered Apr 21 '15 at 13:46

Ajay

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score 1 · Answer 2 · answered Apr 21 '15 at 13:46

You just don't need combined_result as result is already a list. You can return result from your function.

combined_result = []
def executequery(cursor):
    cursor.execute("SELECT id, title FROM database")
    return cursor.fetchall()

combined_result=executequery(sth)

score 1 · Answer 3 · answered Apr 21 '15 at 14:01

1

Try using extend instead of append - instead of treating the list as a single item to append, it takes all the items of one list and adds them to the other:

combined_result.extend(result)

answered Apr 21 '15 at 14:01

Brian L

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what is the difference between extend and append? – Rotan075 Apr 22 '15 at 06:52
I described the difference in my answer - `append` treats the list as a single item; `extend` treats the list as multiple items. See also http://stackoverflow.com/questions/252703/python-append-vs-extend – Brian L Apr 22 '15 at 09:13

Get list out of other list

3 Answers3