books: Add docstrings throughout.

conservancy_beancount/books.py

@@ -1,4 +1,8 @@
-"""books - Tools for loading the books"""
+"""books - Tools for loading the books
+
+This module provides common functionality for loading books split by fiscal
+year and doing common operations on the results.
+"""
 # Copyright © 2020  Brett Smith
 # License: AGPLv3-or-later WITH Beancount-Plugin-Additional-Permission-1.0
 #
@@ -39,10 +43,25 @@ PathLike = Union[str, Path]
 Year = Union[int, datetime.date]
 
 class FiscalYear(NamedTuple):
+    """Convert to and from fiscal years and calendar dates
+
+    Given a month and date that a fiscal year starts, this class provides
+    methods to calculate the fiscal year of a given calendar date; to return
+    important calendar dates associated with the fiscal year; and iterate
+    fiscal years.
+
+    Most methods can accept either an int, representing a fiscal year;
+    or a date. When you pass a date, the method will calculate that date's
+    corresponding fiscal year, and use it as the argument.
+    """
     month: int = 3
     day: int = 1
 
     def for_date(self, date: Optional[datetime.date]=None) -> int:
+        """Return the fiscal year of a given calendar date
+
+        The default date is today's date.
+        """
         if date is None:
             date = datetime.date.today()
         if (date.month, date.day) < self:
@@ -51,14 +70,17 @@ class FiscalYear(NamedTuple):
             return date.year
 
     def first_date(self, year: Year) -> datetime.date:
+        """Return the first calendar date of a fiscal year"""
         if isinstance(year, datetime.date):
             year = self.for_date(year)
         return datetime.date(year, self.month, self.day)
 
     def last_date(self, year: Year) -> datetime.date:
+        """Return the last calendar date of a fiscal year"""
         return self.next_fy_date(year) - datetime.timedelta(days=1)
 
     def next_fy_date(self, year: Year) -> datetime.date:
+        """Return the last calendar date of a fiscal year"""
         if isinstance(year, datetime.date):
             year = self.for_date(year)
         return datetime.date(year + 1, self.month, self.day)
@@ -100,12 +122,25 @@ class FiscalYear(NamedTuple):
 
 
 class LoadResult(NamedTuple):
+    """Common functionality for loaded books
+
+    This class is type-compatible with the return value of the loader
+    functions in ``beancount.loader``. This provides named access to the
+    results, as well as common functionality methods.
+    """
     entries: Entries
     errors: Errors
     options_map: OptionsMap
 
     @classmethod
     def empty(cls, error: Optional[Error]=None) -> 'LoadResult':
+        """Create a return result that represents nothing loaded
+
+        If an error is provided, it will be the sole error reported.
+
+        This method is useful to create a LoadResult when one can't be
+        created normally; e.g., because a books path is not properly configured.
+        """
         errors: Errors = []
         if error is not None:
             errors.append(error)
@@ -116,6 +151,14 @@ class LoadResult(NamedTuple):
             rewrites: Iterable[Union[Path, rewrite.RewriteRuleset]]=(),
             search_terms: Iterable[cliutil.SearchTerm]=(),
     ) -> Iterator[data.Posting]:
+        """Iterate all the postings in this LoadResult
+
+        If ``rewrites`` are provided, postings will be passed through them all.
+        See the ``reports.rewrite`` pydoc for details.
+
+        If ``search_terms`` are provided, postings will be filtered through
+        them all. See the ``cliutil.SearchTerm`` pydoc for details.
+        """
         postings = data.Posting.from_entries(self.entries)
         for ruleset in rewrites:
             if isinstance(ruleset, Path):
@@ -126,9 +169,14 @@ class LoadResult(NamedTuple):
         return postings
 
     def load_account_metadata(self) -> None:
+        """Load account metadata from this LoadResult"""
         return data.Account.load_from_books(self.entries, self.options_map)
 
     def print_errors(self, out_file: TextIO) -> bool:
+        """Report errors from this LoadResult to ``out_file``
+
+        Returns True if errors were reported, False otherwise.
+        """
         for error in self.errors:
             bc_printer.print_error(error, file=out_file)
         try:
@@ -139,6 +187,11 @@ class LoadResult(NamedTuple):
             return True
 
     def returncode(self) -> int:
+        """Return an appropriate Unix exit code for this LoadResult
+
+        If this LoadResult has errors, or no entries, return an exit code that
+        best represents that. Otherwise, return the standard OK exit code 0.
+        """
         if self.errors:
             if self.entries:
                 return cliutil.ExitCode.BeancountErrors
@@ -265,6 +318,11 @@ class Loader:
                 from_fy: Optional[Year]=None,
                 to_fy: Optional[Year]=None,
     ) -> LoadResult:
+        """High-level, "do-what-I-mean"-ish books loader
+
+        Most tools can call this with a books loader from configuration, plus
+        one or two fiscal year arguments, to get the LoadResult they want.
+        """
         if loader is None:
             return cls.load_none()
         elif to_fy is None: