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.)

Resolving patch:
diff --git a/core/domain/stats_jobs_one_off.py b/core/domain/stats_jobs_one_off.py
--- a/core/domain/stats_jobs_one_off.py
+++ b/core/domain/stats_jobs_one_off.py
@@ -27,7 +27,9 @@
 
 
 class StatisticsAudit(jobs.BaseMapReduceJobManager):
-    """Performs a brief audit of exploration completions and state hit counts to
+    """A one-off statistics audit.
+
+    Performs a brief audit of exploration completions and state hit counts to
     make sure they match counts stored in StateCounterModel. It also checks for
     some possible error cases like negative counts.
     """
@@ -41,6 +43,39 @@ def entity_classes_to_map_over(cls):
 
     @staticmethod
     def map(item):
+        """Implements the map function. Must be declared @staticmethod.
+
+        Args:
+            item: ExplorationAnnotationsModel or
+                StateCounterModel.
+
+        Yields:
+            tuple. For StateCounterModel, a 2-tuple in the form
+                (_STATE_COUNTER_ERROR_KEY, error message).
+            tuple. For ExplorationAnnotationModel, a 2-tuple in the form
+                ('exploration_id', value).
+                'exploration_id': str. the id of the exploration.
+                'value': a dict, whose structure is as follows:
+                    {
+                        'version': str. version of the exploration.
+                        'starts': int. # of times exploration was started.
+                        'completions': int. # of times exploration was
+                            completed.
+                        'state_hit': a dict containing the hit counts for the
+                            states in the exploration. It is formatted as
+                            follows:
+                            {
+                                state_name: {
+                                    'first_entry_count': int. # of sessions
+                                        which hit this state.
+                                    'total_entry_count': int. # of total hits
+                                        for this state.
+                                    'no_answer_count': int. # of hits with no
+                                        answer for this state.
+                                }
+                            }
+                    }
+        """
         if isinstance(item, stats_models.StateCounterModel):
             if item.first_entry_count < 0:
                 yield (
@@ -60,6 +95,36 @@ def map(item):
 
     @staticmethod
     def reduce(key, stringified_values):
+        """Updates statistics for the given exploration.
+
+        Args:
+            key: str. The id of the exploration.
+            stringified_values: list(str). A list of stringified values
+                associated with the given key. An element of stringified_values
+                would be of the form:
+                    {
+                        'version': str. version of the exploration.
+                        'starts': int. # of times exploration was started.
+                        'completions': int. # of times exploration was
+                            completed.
+                        'state_hit': dict. a dict containing the hit counts
+                            for the states in the exploration. It is formatted
+                            as follows:
+                            {
+                                state_name: {
+                                    'first_entry_count': int. # of sessions
+                                        which hit this state.
+                                    'total_entry_count': int. # of total
+                                        hits for this state.
+                                    'no_answer_count': int. # of hits with
+                                        no answer for this state.
+                                }
+                            }
+                    }
+
+        Yields:
+            tuple(str). A 1-tuple whose only element is an error message.
+        """
         if key == StatisticsAudit._STATE_COUNTER_ERROR_KEY:
             for value_str in stringified_values:
                 yield (value_str,)


Test patch: