Nsryjdtyk

I'm a freshman in the fantastic world of python and at the moment I'm struggling with this problem...
That's an example of what I've coded:

class League():

    def __init__(self, teams=):

        self.teams = teams

    def initLeague(self):

        for a in range(2):

            self.teams.append(Team())

            self.teams[a].name = "Team" + str(a)

            for b in range(3):

                self.teams[a].players.append(Player())

                self.teams[a].players[b].name = "Name-" + str(a) + "-" + str(b)

    def printLeague(self):

        for team in self.teams:

            print(team.name)

            for player in team.players:

                print(player.name)



class Team():

    def __init__(self, name=None, players=):

        self.name = name

        self.players = players



class Player():

    def __init__(self, name=None):

        self.name = name



nba = League()

nba.initLeague()

nba.printLeague()

The output looks like that:

Team0

Name-1-0

Name-1-1

Name-1-2

None

None

None

Team1

Name-1-0

Name-1-1

Name-1-2

None

None

None

[Finished in 0.051s]

So I would like to know where do these None come from? I noticed they depend on range(n)... it's like if the 'for a' loop is repeating inside the 'for b' loop.
Another problem is that the first part of the output should be:

Team0

Name-0-0

Name-0-1

Name-0-2

...

Could someone help me? Thank you!

If you replace your Team() class to this:

class Team():

def __init__(self, name=None):

    self.name = name

    self.players = 

Your output will become this:

Team0

Name-0-0

Name-0-1

Name-0-2

Team1

Name-1-0

Name-1-1

Name-1-2

which I think is what you're after. See this link: "Least Astonishment" and the Mutable Default Argument to see why.

The problem is that when using your current Team() initialiser, the players parameter is not passed with a default value of as you are expecting, instead, the value of players is persisted for each team made.

Each team has a reference to the same list, which is why the same list is printed twice.

The reason None is printed three times is because each time a team is created, 3 more players are added, but your inner for loop only modifies the names of the first 3 players, leaving the last 3 players untouched.

I agree with 0liveradam8's response and just to add on - if you would like to maintain the constructor signature you could try this:

class Team():

    def __init__(self, name=None, players=None):

        if players is None:

            players = 

        self.name = name

        self.players = players

so you can still specify a list of players in the constructor if necessary.

The reason you are getting None is that you haven't returned the value in the functions. Therefore, when you run your script, it is set to nothing. Here's a link to look into it more.

http://interactivepython.org/runestone/static/pip2/Functions/Returningavaluefromafunction.html

The answer to your second question is that the

for a in range(2):

Should be like

for a in range(1):

Hope this helps!