[Tutor] How to print certain elements

[Mark Lawrence]

On 21/01/2014 10:24, Mkhanyisi Madlavana wrote:
> How would I print washington and monroe using   [:]?
> print X[::3]
> How would I print every element but those two names?
> print X[1::2]
>
>
> On 21 January 2014 12:18, Alan Gauld <alan.gauld at btinternet.com
> <mailto:alan.gauld at btinternet.com>> wrote:
>
>     On 21/01/14 06:18, Adriansanchez wrote:
>
>         Hello everyone,
>         I am newbie to Python and programming in general. My question
>         is, given a list:
>         X=['washington','adams','__jefferson','madison','monroe']
>         And a string:
>         Y='washington,adams,jefferson,__madison,monroe'
>
>         How would I print washington and monroe using   [:]?
>         How would I print every element but those two names?
>
>
>     The [:] syntax is used for selecting a range of values
>     from a starting point to a finish.  Its not appropriate
>     for selecting arbitrary items out of the list.
>
>     If you know which items you want you can use a simple
>     index to access them (remember the first item is index 0)
>
>     So to print the first item and the fourth item:
>
>     print(X[0],X[3])
>
>     In your case it's the first and last so we can do
>     a similar thing:
>
>     print(X[0], X[4])
>
>     But for the last element we can alternatively use
>     a shortcut to save counting the indexes; that's use
>     an index of -1:
>
>     print(X[0],X[-1])
>
>     Printing every element except those two is harder.
>     The simplest approach is to use a loop to process
>     the list and test each value:
>
>     for name in X:
>          if name not in (X[0], X[-1]):
>             print name
>
>     For the special case of excluding the first and
>     last names you could use the [:] notation like
>     this:
>
>     print X[1:-1]
>
>     But that only works where you want *all* the
>     names in a sequence between two end points.
>
>     Finally there is a more advanced way of filtering
>     out items from a list called a list comprehension:
>
>     print ( [name for name in X if name not in (X[0],X[-1])] )
>
>     Which is pretty much our 'for' loop above, written in
>     a shorthand single line form.
>
>     hth
>

If you must top post please get your facts right.

In [1]: X=['washington','adams','jefferson','madison','monroe']

In [2]: print(X[::3])
['washington', 'madison']

In [3]: print(X[1::2])
['adams', 'madison']

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence