On 11/12/2011 03:54 AM, lina wrote:
<SNIP>
The one I tried :
if longest>= 2:
sublist=L1[x_longest-longest:x_longest]
result=result.append(sublist)
if sublist not in sublists:
sublists.append(sublist)
the $ python3 CommonSublists.py
atom-pair_1.txt atom-pair_2.txt
Traceback (most recent call last):
File "CommonSublists.py", line 47, in<module>
print(CommonSublist(a,b))
File "CommonSublists.py", line 24, in CommonSublist
result=result.append(sublist)
AttributeError: 'NoneType' object has no attribute 'append'
in local domain I set the result=[]
I don't know why it complains its NoneType, since the "result" is
nearly the same as "sublists".
Assuming this snippet is part of a loop, I see the problem:
result = result.append(sublist)
list.append() returns none. It modifies the list object in place, but
it doesn't return anything. So that statement modifies the result
object, appending the sublist to it, then it sets it to None. The
second time around you see that error.
In general, most methods in the standard library either modify the
object they're working on, OR they return something. The append method
is in the first category.
--
DaveA
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