Hello everyone. 

I am writing an experiment where the participant chooses between 2 lotteries and receives feedback in the next round. The experiment is set to have 3 treatments and I am coding all treatments in one app. To inform participants about the outcome in round = n I am calling the set_outcome method in round = n before next page. 

In the base treatment this workflow works perfectly. However in the other 2 treatments I receive a Type error. (TypeError: player.outcome is None.) Can anyone help me understand why this is happening? 

The minimal code is below: 

class C(BaseConstants):
    REWARD = 100 # in the storyline points won for each lottery
    
def creating_session(subsession: Subsession):
    # Set balanced treatments
    import itertools
    treatments = itertools.cycle(["Base", "Recommender", "DSS"])
    for player in subsession.get_players():
        player.treatment = next(treatments)

class Player(BasePlayer):
    treatment = models.StringField(doc = "The treatment variable")
    outcome = models.IntegerField(doc = "The outcome of the round for the chosen lottery")
    
def set_outcome(player):
    outcomes = [C.REWARD, 0]
    if player.choice == "A":
        outcome = random.choices(outcomes, weights = (player.lottery_A_success_prob, 1-player.lottery_A_success_prob), k=1)
    else:
        outcome = random.choices(outcomes, weights = (player.lottery_B_success_prob, 1-player.lottery_B_success_prob), k=1)

    player.outcome = int(outcome[0])
    return player.outcome
    
def vars_for_template1(player:Player):
    for p in player.subsession.get_players():
        if p.round_number > 1:
            return dict(previous_outcome = p.in_round(p.round_number - 1).outcome)
            
class Choice(Page):
    form_model = "player"
    form_fields = ["choice"]

    @staticmethod
    def before_next_page(player, timeout_happened):
        set_outcome(player)
        set_recommendation(player)
        set_payoff(player)
        if player.round_number < C.NUM_ROUNDS:
            set_counts(player)

    vars_for_template = vars_for_template1
    
    
According to the error message the line `return dict(previous_outcome = p.in_round(p.round_number - 1).outcome)` is creating the problem. However I don't understand why it works in the base treatment. 

Thank you vey much for your help. 
Ayşegül

Maybe one small additional information. The treatments differ only on the basis of the templates. 

The template, where the treatments are making a difference seem like in the following code: 

{{ block title }}
    Round {{ player.round_number }} of {{ C.NUM_ROUNDS }}
{{ endblock }}
{{ block content }}

    {{ if subsession.round_number < 11 }}
        <p>
            <b> This is a tryout round! </b>
        </p>
    {{ endif }}

    {{ if subsession.round_number > 1 }}
        {{if player.treatment == "Base"}}
            <p>Your outcome in the last round is {{ previous_outcome }}.</p>
        {{ else }}
            {{if player.treatment == "Recommender"}}
                <p>Your outcome in the last round is {{ previous_outcome }}.</p>
                <p>Based on your past choices, the computer recommends you to choose: <b>{{player.recommendation}}</b></p>
            {{ else }}
                {{if player.treatment == "DSS"}}
                    <p>Your outcome in the last round is {{ previous_outcome }}.</p>
                    <p>The table below shows the number of times that lotteries yielded prize according to your choices. </p>

                        <table class="table">
                                <tr>
                                    <th> Lottery A </th>
                                    <th> Lottery B </th>

                                </tr>
                                <tr>
                                    <td>{{player.non_zero_outcome_count_A}}</td>
                                    <td>{{player.non_zero_outcome_count_B}}</td>
                                </tr>

                            </table>
                {{ endif }}
            {{ endif }}
        {{ endif }}
    {{ endif }}

    {{ formfields }}
    {{ next_button }}
    
    
 Apart from these differences in all treatments everything is the same.