Pages¶

Each page that your players see is defined by a Page class in pages.py.

Note

Prior to January 2018, pages.py was called views.py. See oTree 2.0 for more information.

Your pages.py must have a page_sequence variable that gives the order of the pages. For example:

page_sequence = [Start, Offer, Accept, Results]


A Page class can have any of the following optional methods and attributes.

is_displayed()¶

You can define this function to return True if the page should be shown, and False if the page should be skipped. If omitted, the page will be shown.

For example, to only show the page to P2 in each group:

class Page1(Page):
def is_displayed(self):
return self.player.id_in_group == 2


Or only show the page in round 1:

class Page1(Page):
def is_displayed(self):
return self.round_number == 1


If you need to repeat the same rule for many pages, see here. Or try out app_after_this_page.

The code you put in is_displayed() should just return True or False; it should not have any side effects, such as modifying a model field.

vars_for_template()¶

Use this to pass variables to the template. Example:

class Page1(Page):
def vars_for_template(self):
return {
'a': 1 + 1,
'b': self.player.foo * 10
}


Then in the template you can access a and b like this:

Variables {{ a }} and {{ b }} ...


oTree automatically passes the following objects to the template: player, group, subsession, participant, session, and Constants. You can access them in the template like this: {{ Constants.blah }} or {{ player.blah }}.

If you need to pass the same variables to many pages, see here.

Note

You shouldn’t generate random values in vars_for_template, because if the user refreshes their page, vars_for_template will be executed again, and the random calculation might return a different value. Instead, you should calculate random values in either creating_session, before_next_page, or after_all_players_arrive, each of which only executes once.

before_next_page()¶

Here you define any code that should be executed after form validation, before the player proceeds to the next page.

If the page is skipped with is_displayed, then before_next_page will be skipped as well.

Example:

class Page1(Page):
def before_next_page(self):
self.player.tripled_payoff = self.player.bonus * 3


template_name¶

Each Page should have a file in templates/ with the same name. For example, if your app has this page in my_app/pages.py:

class Page1(Page):
pass


Then you should create a file my_app/templates/my_app/Page1.html, (note that my_app is repeated). See Templates for info on how to write an HTML template.

If the template needs to have a different name from your page class (e.g. you are sharing the same template for multiple pages), set template_name. Example:

class Page1(Page):
template_name = 'app_name/MyView.html'


See Timeouts

See Wait pages

Randomizing page sequence¶

You can randomize the order of pages using rounds. An example is here.

app_after_this_page¶

Note

This is an experimental feature in the oTree 2.2 beta, which you can install with pip3 install -U --pre otree.

To skip entire apps, you can define app_after_this_page. For example, to skip to the next app, you would do:

class MyPage(Page):
def app_after_this_page(self, upcoming_apps):
if self.player.whatever:
return upcoming_apps[0]


upcoming_apps is the remainder of the app_sequence (a list of strings). Therefore, to skip to the last app, you would return upcoming_apps[-1]. Or you could just return a hardcoded string (as long as that string is in upcoming_apps):

class MyPage(Page):
def app_after_this_page(self, upcoming_apps):
print('upcoming_apps is', upcoming_apps)
if self.player.whatever:
return "public_goods"


If this function doesn’t return anything, the player proceeds to the next page as usual.