Inserting lists to a nested-list within a for-loop in Python

Question

as a project to get used to writing in Python (the only language I have any knowledge of at the moment) I am writing a Cribbage score counter.

I have found all of the 3, 4 and 5 length subsets from a set of 5 numbers. The subsets are all sorted into numerical order. The function below is supposed to find the subsets which are numbers in order eg [1, 2, 3] or [3, 4, 5].

def straight_counter(subset, length):
    straights = []
    a = 0  # Variable for incremental increase
    for i in range(0, length - 2):  # Select one of the first three numbers of    a set of 3-5 (which are already ordered)
        run = 1
        x = 1

        while i + x < length:  # Ensure that we do not go beyond the final index

            if subset[i + x - 1] + 1 == subset[i + x]:  # Is the next number one greater than the currently selected number

                run += 1  # Count how many numbers we have in order (will be maximum of 5)
                x += 1

            else:
                break

Here is where I try to get only the subsets which are all numbers in order. But when I attempt to add the into a nested list I keep writing over the first index of the list each time and the list is only ever one item long when I print it

            if run == length:  # If the run of consecutive numbers uses all of the numbers e.g [1, 2, 3] and not [1, 2, 4]

                straights.insert(a, subset)  # I would like to add the list as the first index of a different list

                a += 1  # Increase a so that the next valid subset will be at the next index
                print(straights)

Is there an obvious reason why this is happening? Or maybe there's a much neater way of attempting this. Thanks

For example from the input list of numbers

[1, 1, 2, 3, 4]

I am attempting to create a nested list of:

[[1, 2, 3], [1, 2, 3], [2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]].

Which are all the sets of consecutive numbers of length 3 or greater.

Answer 1

You can find below a solution. The idea is to find the first and last number of consecutive sets.

# -*-coding:Utf-8 -*

data = [1, 4, 5, 6, 10, 15, 16, 17, 18, 22, 25, 26, 27, 28]

from operator import itemgetter
from itertools import groupby

for k, g in groupby(enumerate(data), lambda ix : ix[0] - ix[1]):
    group = list(map(itemgetter(1), g))
    print ((group[0], group[-1]))

At this point you get this :

(1, 1)
(4, 6)
(10, 10)
(15, 18)
(22, 22)
(25, 28)

Then you simply need to select the right ones and to keep them (difference above 2). You can also recreate a list if needed.

Answer 2

OP: You're mentioning 5 cards, which would be a 'kept hand' + starter or crib + starter. What about when there are more? Specifically, The Play. Looking ahead, should the same piece of code be used for both purposes?

Imagine players have A-3-5-7 and 2-3-4-6

The maximum count would be (1+3+5+7)+(2+3+4+6) => 31. Whilst there's a finite number of combinations and the order in which the cards are played, it's a bit trickier.

BTW: as a bit (pun intended) of Cribbage trivia, The Sting will be on Flix (09/02) and Showtime (09/07). It's one of the few places you'll see Cribbage played onscreen.