In the follwoing code, Why the result is "'defenestrate', 'window', 'defenestrate', " before the original list instead of 'defenestrate', 'window', ?
>>> a = ['defenestrate', 'cat', 'window', 'defenestrate'] >>> for x in a[:]: ... if len(x) > 4: a.insert(0, x) ... >>> a ['defenestrate', 'window', 'defenestrate', 'defenestrate', 'cat', 'window', 'defenestrate'] On 10/25/05, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > Shi Mu wrote: > > >I can not understand the use of "cell" and "row" in the code: > > > > # convert the matrix to a 1D list > > matrix = [[13,2,3,4,5],[0,10,6,0,0],[7,0,0,0,9]] > > items = [cell for row in matrix for cell in row] > > print items > > working through the Python tutorial might be a good idea. here's the section > on list comprehensions: > > http://docs.python.org/tut/node7.html#SECTION007140000000000000000 > > and here's the section on for loops: > > http://docs.python.org/tut/node6.html#SECTION006200000000000000000 > > briefly: > > items = [cell for row in matrix for cell in row] > > or, slightly edited for clarity: > > items = [(cell) > for row in matrix > for cell in row] > > is the same thing as: > > items = [] > for row in matrix: > for cell in row: > items.append(cell) > > except that it's a bit shorter, and a bit more efficient. > > </F> > > > > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
