Python Nested List Creation

Question

import random

class player():
    def __init__(self, deck):
        self.deck = deck 
        self.hand = []
        self.results = []

    def draw(self,draws):
        for counter in range(0, draws, 1):
            card = random.randrange(0, len(self.deck), 1)
            self.hand.append(self.deck[card])
            del self.deck[card]

    def return_hand(self):
        for returncounter in range(0, len(self.hand), 1):
            self.deck.append(self.hand[returncounter]) 
        for returncounter in range(0, len(self.hand), 1):
            del self.hand[0]

    def simple_function(self):
        for counter in range(0, 3, 1):
            print("Loop", counter)
            self.draw(3)
            print("Hand", simple_cards.hand)
            self.results.extend(self.hand)
            print("Results before return", simple_cards.results)
            self.return_hand()
            print("Results after return", simple_cards.results)
            print("")

simple_cards = player(["A1", "A2", "A3", "B1", "B2", "B3", "C1", "C2", "C3"])

simple_cards.simple_function()
print("Results after function", simple_cards.results)

An Example result from this code would be

Loop 0
Hand ['B3', 'B2', 'C3']
Results before return ['B3', 'B2', 'C3']
Results after return ['B3', 'B2', 'C3']

Loop 1
Hand ['C2', 'B3', 'A1']
Results before return ['B3', 'B2', 'C3', 'C2', 'B3', 'A1']
Results after return ['B3', 'B2', 'C3', 'C2', 'B3', 'A1']

Loop 2
Hand ['C2', 'B2', 'C1']
Results before return ['B3', 'B2', 'C3', 'C2', 'B3', 'A1', 'C2', 'B2', 'C1']
Results after return ['B3', 'B2', 'C3', 'C2', 'B3', 'A1', 'C2', 'B2', 'C1']

Results after function ['B3', 'B2', 'C3', 'C2', 'B3', 'A1', 'C2', 'B2', 'C1']

How do I make the result 3 nested lists like [['B3', 'B2', 'C3'], ['C2', 'B3', 'A1'], ['C2', 'B2', 'C1']]

I feel like there is a pretty fundamental thing I'm not understanding here and that this question has certainly already been answered but I don't know how to frame the question better to find it by searching myself.

I tried append(self.hand) and extend([self.hand]) but both created more problems than they solved resulting in an example output of

Loop 0
Hand ['B3', 'A2', 'B2']
Results before return [['B3', 'A2', 'B2']]
Results after return [[]]

Loop 1
Hand ['B2', 'B3', 'C3']
Results before return [['B2', 'B3', 'C3'], ['B2', 'B3', 'C3']]
Results after return [[], []]

Loop 2
Hand ['C2', 'B3', 'A2']
Results before return [['C2', 'B3', 'A2'], ['C2', 'B3', 'A2'], ['C2', 'B3', 'A2']]
Results after return [[], [], []]

Results after function [[], [], []]

Thanks for any help.

niemmi · Accepted Answer · 2016-12-10 01:40:37Z

1

You can use append to add the copy of the hand to results. The problem with just appending the hand is that you're modifying it later with del which will be reflected to the printed results as your example shows.

If you change self.results.extend(self.hand) to self.results.append(self.hand[:]) you get following output:

Loop 0
Hand ['A1', 'C2', 'B3']
Results before return [['A1', 'C2', 'B3']]
Results after return [['A1', 'C2', 'B3']]

Loop 1
Hand ['B1', 'B3', 'A1']
Results before return [['A1', 'C2', 'B3'], ['B1', 'B3', 'A1']]
Results after return [['A1', 'C2', 'B3'], ['B1', 'B3', 'A1']]

Loop 2
Hand ['C2', 'B1', 'C1']
Results before return [['A1', 'C2', 'B3'], ['B1', 'B3', 'A1'], ['C2', 'B1', 'C1']]
Results after return [['A1', 'C2', 'B3'], ['B1', 'B3', 'A1'], ['C2', 'B1', 'C1']]

Results after function [['A1', 'C2', 'B3'], ['B1', 'B3', 'A1'], ['C2', 'B1', 'C1']]

answered Dec 10, 2016 at 1:40

niemmi

17.3k7 gold badges38 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Diofsi Over a year ago

Thanks thats exactly the sort of solution I was looking for :). Is there any specific part of python documentation/tutorials I could look at that might help make it clear when I am making something point to another variable versus creating an entirely new value? I think I learn through trial and error too much because I only partially understand the terminology used in python documentation so reading it doesn't make things as clear as it should.

niemmi Over a year ago

@Diofsi You can check glossary for various terms used in documentation. You could try to read Data model from Python reference for explanation on immutable vs mutable objects. In short you can always refer the documentation when calling a method to see if it mutates the object or not.

Chiheb Nexus · Accepted Answer · 2016-12-10 02:05:40Z

1

You can also keep your code like what it is right now, and split only the results.

For example, i assume that your output is:

output = ['B3', 'B2', 'C3', 'C2', 'B3', 'A1', 'C2', 'B2', 'C1']

So, you can do something like this:

expected_output = [output[i:i+3] for i in range(0, len(output), 3)]
print(expected_output)

Output:

[['B3', 'B2', 'C3'], ['C2', 'B3', 'A1'], ['C2', 'B2', 'C1']]

So, in order to edit your code, you have only to edit one line:

self.results.extend(self.hand) to self.results.extend(self.hand[i:i+3] for i in range(0, len(self.hand), 3))

So your simple_function() will be:

def simple_function(self):
        for counter in range(0, 3, 1):
            print("Loop", counter)
            self.draw(3)
            print("Hand", simple_cards.hand)
            # The edited line
            self.results.extend(self.hand[i:i+3] for i in range(0, len(self.hand), 3))
            print("Results before return", simple_cards.results)
            self.return_hand()
            print("Results after return", simple_cards.results)
            print("")

Output after the edit:

Loop 0
Hand ['B1', 'C1', 'C3']
Results before return [['B1', 'C1', 'C3']]
Results after return [['B1', 'C1', 'C3']]

Loop 1
Hand ['C1', 'C3', 'A3']
Results before return [['B1', 'C1', 'C3'], ['C1', 'C3', 'A3']]
Results after return [['B1', 'C1', 'C3'], ['C1', 'C3', 'A3']]

Loop 2
Hand ['C2', 'A3', 'B3']
Results before return [['B1', 'C1', 'C3'], ['C1', 'C3', 'A3'], ['C2', 'A3', 'B3']]
Results after return [['B1', 'C1', 'C3'], ['C1', 'C3', 'A3'], ['C2', 'A3', 'B3']]

Results after function [['B1', 'C1', 'C3'], ['C1', 'C3', 'A3'], ['C2', 'A3', 'B3']]

edited Dec 10, 2016 at 2:05

answered Dec 10, 2016 at 1:45

Chiheb Nexus

9,2774 gold badges33 silver badges45 bronze badges

3 Comments

Diofsi Over a year ago

Thanks :). The line of code itself seems more complex than niemmis example but it allows more intricate slicing of the results which is useful if I don't want the entire self.hand

Chiheb Nexus Over a year ago

Yes, you can split your list within the steps you like. So you can undernstand it like this [output[i:i+step] for i in range(0, len(output), step)] and this line mean: return a list of slices which are from output from the range i to step for every i in the range between 0 and length of output but with a step. For example for k in range(0,7,3) , k will be: 0,3 and 6.

Chiheb Nexus Over a year ago

Also, be sure that you can respond to any question within different manners. You have the choice to use any method you want that you can easly understand.

Collectives™ on Stack Overflow

Python Nested List Creation

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related