How to generically transform a list?

[Daniel Yoo]

Marco Aschwanden <PPNTWIMBXFFC at spammotel.com> wrote:

: Suppose you have a list of lists:

: theList = [['a',1,11,'aa'], ['b',2,22,'bb'],['c',3,33,'cc']]

: I would like to have a GENERIC way how to turn this list of list into 
: another list of list.
: - A user can choose which columns she wants
: - A user can select the order of the columns


It sounds like you want something like the 'cut' Unix command.  Here's
one way to do it.

###
def cut(iterable, columns):
    """Selects columns from the iterable."""
    for row in iter(iterable):
        yield(tuple([row[i] for i in columns]))
###



For example:

###
>>> l = [['1', '2', '3'],
...      ['a', 'b', 'c'],
...      ['ka', 'na', 'da']]
>>>
>>> for row in cut(l, (2, 0, 1)): print row
...
('3', '1', '2')
('c', 'a', 'b')
('da', 'ka', 'na')
>>>
>>> for row in cut(l, (2, 1)): print row
...
('3', '2')
('c', 'b')
('da', 'na')
###


Hope this helps!