Working with lists of pages

Templates which render a list of content files (e.g. a list of blog posts or pages belonging to a category) will need to filter or sort MDCONTENT accordingly. In order to make this easier, MDCONTENT is wrapped in a list-like object called MDContentList, which has the following methods:

General searching/filtering

Each of the following methods returns a new MDContentList containing those entries for which the predicate (pred) is True.

• match_entry(self, pred): The pred (i.e. predicate) is a callable which receives the full information on each entry in the MDContentList and returns True or False.

• match_ctx(self, pred): The pred receives the context for each entry and returns a boolean.

• match_page(self, pred): The pred receives the page object for each entry and returns a boolean.

• match_doc(self, pred): The pred receives the markdown body for each entry and returns a boolean.

• url_match(self, url_pred): The pred receives the url (relative to htdocs) for each entry and returns a boolean.

• path_match(self, src_pred): The pred receives the path to the source document for each entry and returns a boolean.

Specialized searching/filtering

All of these return a new MDContentList object (at least by default).

• posts(self, ordered=True): Returns a new MDContentList with those entries which are blog posts. In practice this means those with markdown sources in the posts/ or blog/ subdirectories or those which have a page.type of "post", "blog", "blog-entry" or "blog_entry". Normally ordered by date (newest first), but this can be turned off by setting ordered to False.

• not_posts(self): Returns a new MDContentList with "pages", i.e. those entries which are not blog posts.

• has_slug(self, sluglist), has_id(self, idlist): Entries with specific slugs/ids.

• in_date_range(self, start, end, date_key='DATE'): Posts/pages with a date between start and end. The key for the date field can be specifed using date_key. Unless the value for date_key is either DATE or MTIME, then the key is looked for in the page variables for the entry.

• has_taxonomy(self, haystack_keys, needles): A general search for entries belonging to a taxonomy group, such as category, tag, section or type. They haystack_keys are the page variables to examine while needles is a list of the values to look for in the values of those variables. A string value for needles is treated as a one-item list. The search is case-insensitive.

• in_category(self, catlist): A shortcut method for self.has_taxonomy(['category', 'categories'], catlist)

• has_tag(self, taglist): A shortcut method for self.has_taxonomy(['tag', 'tags'], taglist).

• in_section(self, sectionlist): A shortcut method for self.has_taxonomy(['section', 'sections'], sectionlist).

• group_by(self, pred, normalize=None, keep_empty=False): Group items in an MDContentList using a given criterion. Parameters: pred is a callable receiving a content item and returning a string or a list of strings. For convenience, pred may also be specified as a string and is then interpreted as the value of the named page variable, e.g. category; normalize is an optional callable that transforms the grouping values, e.g. by truncating and lowercasing them; keep_empty should be set to True when the content items whose predicate evaluates to the empty string are to be included in the result, since they otherwise will be omitted. Returns a dict whose keys are strings and whose values are MDContentList instances.

• page_match(self, match_expr, ordering=None, limit=None): This is actually quite a general matching method but does not require the caller to pass a predicate callable to it, which means that it can be employed in more varied contexts than the general methods described in the last section. A match_expr contains the filtering specification. It will be described further below. The ordering parameter, if specified, should be either title, slug, url or date, with an optional - in front to indicate reverse ordering. The date option for ordering may be followed by the preferred frontmatter date field after a colon, e.g. ordering='-date:modified_date' for a list with the most recently changed files at the top. The limit, if specified, obviously indicates the maximum number of pages to return.

• page_match_sql(), get_db(), get_db_columns() – see "Searching/filtering using SQL" below.

A match_expr for page_match() is either a dict or a list of dicts. If it is a dict, each page in the result set must match each of the attributes specified in it. If it is a list of dicts, each page in the result set must match at least one of the dicts (i.e., the returned result set contains the union of all matches from all dicts in the list). When a string or regular expression match is being performed in this process, it will be case-insensitive. The supported attributes (i.e. dict keys) are as follows:

• title: A regular expression which will be applied to the page title.
• slug: A regular expression which will be applied to the slug.
• id: A string or list of strings (one of) which must match the page id exactly.
• url: A regular expression which will be applied to the target URL.
• path: A regular expression which will be applied to the path to the markdown source file (i.e. the source_file_short field).
• doc: A regular expression which will be applied to the body of the markdown source document.
• date_range: A list containing two ISO-formatted dates and optionally a date key (DATE by default) - see the description of in_date_range() above.
• has_attrs: A list of frontmatter variable names. Matching pages must have a non-empty value for each of them.
• attrs: A dict where each key is the name of a frontmatter variable and the value is the value of that attribute. If the value is a string, it will be matched case-insensitively. All key-value pairs must match.
• has_tag, in_section, in_category: The values are lists of tags, sections or categories, respectively, at least one of which must match (case-insensitively). See the methods with these names above.
• is_post: If set to True, will match if the page is a blog post; if set to False will match if the page is not a blog post.
• exclude_url: The page with this URL should be omitted from the results (normally the calling page).

Searching/filtering using SQL

An MDContentList has three methods for examining the content using an SQLite in-memory database:

• get_db(self): Builds a SQLite database containing a single table, content, whose structure is described below. Returns a connection to this database which can then be worked with using normal sqlite3/DBAPI methods. The database has a locale-sensitive collation called locale (which applies locale.strxfrm) and a custom function casefold (which simply applies the Python casefold string method). The row factory is sqlite3.Row, so row fields can be read using either column names or integer indices.

• get_db_columns(self): Returns a simple list of the columns in the content table.

• page_match_sql(self, where_clause=None, bind=None, order_by=None, limit=None, offset=None, raw_sql=None, raw_result=False, first=False): Either where_clause or raw_sql must be specified. In either case, if bind is specified, the bind variables there will be applied to the SQL upon execution. If order_by (a string), limit or offset (integers) are specified, they will be appended to the SQL before executing it against the database connection. The result will be a MDContentList unless raw_result is True, in which case it is a cursor object. (If raw_result is False but raw_sql is supplied, the column list in the SQL select statement must include source_file so as to permit the construction of an appropriate MDContentList). If first is True, only the first item from the results is returned (or None, if the results are empty).

The content table constructed by get_db() always contains the columns source_file, source_file_short, url target, template, MTIME, DATE, doc, and rendered. In addition, it contains each page metadata field that appears in any of the entries in the MDContentList in question. These will be added as columns with the page_ prefix; for instance, the title field will become page_title.

It should be noted that all page fields added to the table will have to match the regular expression ^[a-z]\w*$. Thus, any metadata field with a key that is all uppercase, titlecased, or contains non-word characters (such as hyphens) will be omitted. Also, field names are case-sensitive in the raw metadata, but case-insensitive in the database table, so inconsistently capitalized field names may lead to unexpected results.

A field value that is not either string, integer, float, boolean, date, datetime, or None, will be serialized using json.dumps() with ensure_ascii set to False (for easier utf-8 matching). Dates and datetimes are stringified. Booleans will be represented as 1 or 0.

Sorting

All of these return a new MDContentList object with the entries in the specified order.

• sorted_by(self, key, reverse=False, default_val=-1): A general sorting method. The key is the page variable to sort on, default_val is the value to assume if there is no such variable present in the entry, while reverse indicates whether the sort is to be descending (True) or ascending (False, the default).

• sorted_by_date(self, newest_first=True, date_key='DATE'): Sorting by date, newest first by default. The date key to sort on can be specified if desired.

• sorted_by_title(self, reverse=False): Sorting by page.title, ascending by default.

Pagination

• paginate(self, pagesize=5, context=None): Divides the MDContentList into chunks of size pagesize and returns a tuple consisting of the chunks and a list of page_urls (one for each page, in order). If an appropriate template context is provided, pages 2 and up will be written to the webroot output directory to destination files whose names are based upon the URL for the first page (and the page number, of course). Without the context, the page_urls will be None. It is the responsibility of the calling template to check the _page variable for the current page to be rendered (this defaults to 1). Each iteration will get all chunks and must use this variable to limit itself appropriately.

Typical usage of paginate():

<%
  posts = MDCONTENT.posts()
  chunks, page_urls = posts.paginate(5, context)
  curpage = context.get('_page', 1)
%>

% for post in chunks[curpage-1]:
  ${ show_post(post) }
% endfor

% if len(chunks) > 1:
  ${ prevnext(len(chunks), curpage, page_urls) }
% endif

Render to an arbitrary file

• def write_to(self, dest, context, extra_kwargs=None, template=None): Calls a template with the MDContentList in self as the value of CHUNK and write the result to the file named in dest. The file is of course relative to the webroot. Any directories are created if necessary. The template is by default the calling template while extra_kwargs may be added if desired.

Typical usage of write_to():

<%
  if not CHUNK:
     for tag in tags:
         tagged = MDCONTENT.has_tag([tag])
         if not tagged:
             continue  # avoid potential infinite loop!
         outpath = '/tags/' + slugify(tag) + '/index.html'
         tagged.write_to(outpath, context, {'TAG': tag})
%>

% if CHUNK:
  ${ list_tagged_pages(TAG, CHUNK) }
% else:
  ${ list_tags() }
% endif