First-off, it has to be said that "100's of elements" suggests using an
RDBMS - particularly if 'age' (eg 23 and 99) is not the only likely
selection mechanism.
On 7/07/19 2:39 PM, mhysnm1...@gmail.com wrote:
Hi all.
In C, you can use pointers to reference variables, arrays, ETC. In python, I
do not recall anything specifically that refers to such a capability. What I
want to do is:
Just because C has a construct does not imply that it does, nor even
should, exist in another language! You're using Python because it is
'better', right?
You are correct, Python does not use "pointers", and (a personal
comment) I for one don't miss them and their many 'gotchas', eg
out-by-one errors, preferring Python's constructs, eg for-each.
That said, Python's sequences (data structures, eg strings and lists) do
offer indices, slicing, and striding. So, it is quite possible to
(relatively) address the first item in a list as list_item[ 0 ]. You can
read about these (and many other delights) in the docs...
I want to create different data structures such as dictionaries which
contain specific list elements based upon specific keys. The original data
structure could look like:
Data = [
['2019-01-19','Fred Flintstone',23],
['2019-02-01','Scooby doo', 99]
]
Warning1: seem to be missing any identification of the "key"
Warning2: the intro text talked about "dictionaries" (the correct word)
but the code-snippet is describing nested lists
The above structure does have 100's of elements. I want to reference
specific lists within the above structure. Using the only method I know how:
Category = {'under-50':[data[0]], 'over-50':[data[1]]}
If I understand things correctly with Python. The above will copy the value
into the list within the key. Not the memory address of the nested list I am
referencing. I am using a list within the key to permit multiple references
to different nested lists from the original data structure. The end result
of the structure for the dict could look like this (using example, not real
output)
Category['under-50'] = [ List1 pointer, List22 pointer, List52 pointer]
I hope the above makes sense. How can this be done?
I hope I've understood the description! One option would be to follow
your line of thinking by turning the first data-structure into a
dictionary (key-value) pairs, where the key is the character's age and
the value is the inner list structure, previously outlined:
{
23: ['2019-01-19','Fred Flintstone',23],
99: ['2019-02-01','Scooby doo', 99]
}
Then it would be possible to maintain the two lists, each containing
keys for the relevant dict-elements:
under_50 = [ 23 ]
over_50 = [ 99 ]
However, this would require that only one character be listed at a given
age (dict keys must be unique), so another key might be a better choice!
Another data structure you might consider is a "linked list".
--
Regards =dn
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