Repository: oppia/oppia

Issue:
Update docstrings in the Python backend code to follow the style guide.
We've been a bit lax about adding docstrings to code in the backend. Instead, we should be following the style guide: https://google.github.io/styleguide/pyguide.html?showone=Comments#Comments -- docstrings should define args, return values, exceptions, etc. The aim of this issue is to ensure that the backend code is properly documented; we will tackle this on a file-by-file basis.

Note: if you're a new contributor, this issue is a particularly good introductory one to tackle, since it will require reading, understanding and documenting the purpose of a file in the codebase, and help you get acquainted with how the Oppia backend is structured. It's important that you're able to communicate and write clearly, though!

Some useful tips:
-  Please follow our [style guide](https://github.com/oppia/oppia/wiki/Coding-style-guide#general) (and also the [Google Python style guide](https://google.github.io/styleguide/pyguide.html?showone=Comments#Comments)) when writing docstrings. Make sure to follow the patterns established there as closely as possible, including spacing, capitalization and punctuation. Also, it's a good idea to look at some of the existing files (see below) to get a sense of the correct format -- we recommend following this closely in order to maintain uniformity across the codebase.
- If applicable, make sure that the docstrings for all functions correctly specify the args, return values, etc. If a function has no args, you can omit the Args section; if it has no return value, you can omit the Returns section.
- If a docstring is not present in the code, or the existing one is too vague for you to understand what's going on just by looking at it, then it should be rewritten to be more clear. You'll often need to read the code as well, and do a grep on the callsites to see how it's being used, in order to get a clear understanding of what it's doing. This is good practice for learning how to navigate the codebase, and is an intended part of this project.
- If you feel that parts of the codebase are unclear or incorrectly factored, please feel free to bring this up! The whole point of docstrings is to improve code health and accessibility for new developers, so if you spot other things that can be done in service of that aim, we should also look into doing that.

**Completed:**
- [x] core.controllers.base @shaz13 
- [x] core.controllers.cron @saeedjassani
- [x] core.controllers.reader @96mohitm
- [x] core.domain.activity_domain @andromfins
- [x] core.domain.activity_services @souravsingh
- [x] core.domain.classifier_services @andromfins 
- [x] core.domain.collection_domain @domevit
- [x] core.domain.collection_services @kahkhang 
- [x] core.domain.config_services @vibhor98 
- [x] core.domain.email_manager @Oishikatta 
- [x] core.domain.exp_domain @domevit
- [x] core.domain.exp_services @DubeySandeep
- [x] core.domain.feedback_domain @terrameijar 
- [x] core.domain.feedback_jobs_continuous
- [x] core.domain.feedback_services @andimeo
- [x] core.domain.fs_domain @kartik-25 
- [x] core.domain.html_cleaner @seanlip
- [x] core.domain.param_domain @rohan-gulati
- [x] core.domain.rating_services @BojOnTheBeat 
- [x] core.domain.rights_manager @ayejay
- [x] core.domain.stats_domain @Arunabh98
- [x] core.domain.stats_jobs_continuous @Arunabh98 
- [x] core.domain.stats_jobs_one_off @zpuller
- [x] core.domain.stats_services @manoj-makkuboy 
- [x] core.domain.subscription_services @vibhor98 
- [x] core.domain.summary_services @domevit 
- [x] core.domain.user_jobs_continuous @shubha1593 
- [x] core.domain.user_services @Nalinc 
- [x] core.domain.value_generators_domain @meetsha 
- [x] core.jobs @brianrodri
- [x] core.platform.app_identity.gae_app_identity_services @ubhisat
- [x] core.platform.models @pranavsid98 
- [x] core.platform.transactions.gae_transaction_services @ubhisat
- [x] core.storage.base_model.gae_models @vojtechjelinek
- [x] core.storage.collection.gae_models @kaggis
- [x] core.storage.email.gae_models @rajan-garg
- [x] core.storage.exploration.gae_models @kirankonduru
- [x] core.storage.feedback.gae_models @naveenshukla
- [x] core.storage.file.gae_models @Ian91 
- [x] core.storage.job.gae_models @sasacocic
- [x] core.storage.statistics.gae_models @abhishekarya286
- [x] core.storage.user.gae_models @Anthony-Alridge 
- [x] core.tests.test_util_jobs @seanlip
- [x] core.tests.test_utils @vibhor98
- [x] utils @yashLadha 


Discussion:
@seanlip I would like to work in the issue.

Hi @souravsingh, do you think you could finish up #2051 first, please? Thanks! 

@seanlip I would like to work on this issue.

Hi @andromfins -- now that you've had a go at writing docstrings for a single class, would you mind picking one or two other files and doing the same thing for those? Let me know which ones you pick, so that I can mark you off against them.

Thanks!

Hi, i'm working on **core.domain.classifier_services**.

OK, thanks @andromfins! 

@seanlip Can I take a stab at other file to add docstrings?

Yep, sounds good. Could you take core.domain.html_cleaner? Thanks!

@andromfins -- are you still working on this?

  @seanlip Yes!

I would like to work on `core.domain.stats_domain`

@Arunabh98 assigned you on `core.domain.stats_domain`

Almost completed `core.domain.stats_domain`. Now working on `core.domain.stats_jobs_continuous`

hi @seanlip 
I am working on this issue.
I am writing the docstrings for /core/storage/collection/gae_models.py as i was assigned as a starting project.

@seanlip can I work on core.controllers.cron?
Yep, sounds good! I've updated the list.
@seanlip I'd like to work on core.storage.job.gae_models.
Sounds good, thanks @sasacocic! I've updated the list. 
@seanlip I'd like to work on core.platform.models. Thanks

@seanlip I'd like to work on core.domain.stats_services
Sounds good, thanks @arjunmahishi! I've assigned you. 
@seanlip I'd like to work on core.domain.summary_services
Sounds good, thanks! I've assigned you.
@seanlip Hello, i would work on core.domain.config_domain if possible.
@tvallois I have assigned you to that. Thanks
@seanlip I can do core.domain.rights_manager.py
Sounds good @fodra, I've assigned you. Thanks! 
@seanlip I would like to take _core.tests.test_util_jobs_
Sounds great, I've assigned you. Thanks @terrameijar! 
@seanlip could i work on  core.storage.statistics.gae_models?

I'd like to contribute to this, could you please assign me one of the sub tasks?
Hi @fsam95, welcome to Oppia! Could you please follow the instructions [here](https://github.com/oppia/oppia/wiki/Contributing-code-to-Oppia#setting-things-up) first?

@cosmicAsymmetry The list of tasks that are yet to be done is in the "Not started" section. Would you be up for taking a look at the corresponding files, and picking one that looks approachable? Note that test_utils has some prior work that you might be able to extend, though it's slightly unusual because the functions within it are meant mainly for supporting backend testing (and are therefore not directly user-facing). Thanks!
I've followed the instructions :). 
Thanks @fsam95! Assigned you. 
@seanlip I want to take one of the files but it looks like all the files in "Not started" section have been documented? Can you assign me to one which has not been taken? Thanks! :)
Hi @zhengxit -- actually, all those files still need work, I think, be it improving the existing docstrings, writing new docstrings for methods/functions which don't have them, or making sure that everything follows the correct style. So, please feel free to pick one of them!
(P.S. If you see a particular file in the "Not started" section that you're not sure what to do with, just ask.)
@seanlip I would like to take **core.controllers.base**

Assigned. Thanks @shaz13! 
I'm starting work on **core.jobs**.
@seanlip Please assign me an issue.I also want to contribute.
can I take #2394 Docstrings for controllers/base.py
@seanlip I am taking core.domain.stats_services
OK, thanks! Assigned you.
hey...I am working on core.domain.stats_services....I can see previous docstrings in it.So, what exactly is incomplete in this project.
Hello @arjunsuri, you can look at the previous PRs' ( alike #3448, #2459 ) to get an idea about expected format. I looked into the file [core.domain.stats_services. ](https://github.com/oppia/oppia/blob/develop/core/domain/stats_services.py) there are still few functions missing Args, Return information which you should document in your PR. If you still have any doubts feel free to ping us in the Gitter channel. 

Resolving patch:
diff --git a/core/domain/feedback_jobs_continuous.py b/core/domain/feedback_jobs_continuous.py
--- a/core/domain/feedback_jobs_continuous.py
+++ b/core/domain/feedback_jobs_continuous.py
@@ -35,7 +35,8 @@ class FeedbackAnalyticsRealtimeModel(
 
 class FeedbackAnalyticsAggregator(jobs.BaseContinuousComputationManager):
     """A continuous-computation job that computes analytics for feedback
-    threads of explorations."""
+    threads of explorations.
+    """
 
     @classmethod
     def get_event_types_listened_to(cls):
@@ -52,6 +53,16 @@ def _get_batch_job_manager_class(cls):
 
     @classmethod
     def _handle_incoming_event(cls, active_realtime_layer, event_type, *args):
+        """Records thread analytics in the given realtime layer.
+
+        Args:
+            active_realtime_layer: int. The currently active realtime
+                datastore layer.
+            event_type: str. The event triggered by the student.
+            *args: Variable length argument list. The first element of *args
+                corresponds to the id of the exploration currently being
+                played.
+        """
         exp_id = args[0]
 
         def _increment_open_threads_count():
@@ -118,13 +129,20 @@ def _decrement_open_threads_count():
     # Public query methods.
     @classmethod
     def get_thread_analytics_multi(cls, exploration_ids):
-        """
-        Args:
-          - exploration_ids: ids of the explorations to get statistics for.
+        """Gets the thread analytics for the explorations specified by the
+        exploration_ids.
 
-        Returns a list of dicts, each with two keys: 'num_open_threads' and
-        'num_total_threads', representing the counts of open and all feedback
-        threads, respectively.
+        Args:
+            exploration_ids: list(str). IDs of the explorations to get
+            analytics for.
+
+        Returns:
+            list(dict). Each dict in this list corresponds to an
+            exploration ID in the input list, and has two keys:
+            - num_open_threads: int. The count of open feedback threads
+              for this exploration.
+            - num_total_threads: int. The count of all feedback threads
+              for this exploration.
         """
         realtime_model_ids = cls.get_multi_active_realtime_layer_ids(
             exploration_ids)
@@ -148,13 +166,17 @@ def get_thread_analytics_multi(cls, exploration_ids):
 
     @classmethod
     def get_thread_analytics(cls, exploration_id):
-        """
-        Args:
-         - exploration_id: id of exploration to get statistics for
-
-        Calls get_thread_analytics_multi internally and returns a dict with two
-        keys - 'num_open_threads' and 'num_total_threads'.
+        """Retrieves the analytics for feedback threads.
 
+        Args:
+            exploration_id: str. ID of exploration to get statistics for.
+
+        Returns:
+            dict with two keys:
+            - num_open_threads: int. The count of open feedback threads for
+              this exploration.
+            - num_total_threads: int. The count of all feedback
+              threads for this exploration.
         """
         return FeedbackAnalyticsAggregator.get_thread_analytics_multi(
             [exploration_id])[0]
@@ -179,10 +201,27 @@ def entity_classes_to_map_over(cls):
 
     @staticmethod
     def map(item):
+        """Map function.
+
+        Args:
+            item: FeedbackThreadModel. A feedback thread model instance.
+
+        Yields:
+            A tuple of two elements:
+              - str. The exploration id associated to the feedback thread.
+              - str. The feedback thread's status.
+      """
         yield (item.exploration_id, item.status)
 
     @staticmethod
     def reduce(key, stringified_values):
+        """Reduce function.
+
+        Args:
+            key: str. The exploration ID.
+            stringified_values: list(str). List of all statuses from all
+                mappers tagged with the given key.
+      """
         num_open_threads = stringified_values.count(
             feedback_models.STATUS_CHOICES_OPEN)
         num_total_threads = len(stringified_values)


Test patch: