webapp的Django模版引擎 - rain.j

调用格式：template.render(path, template_values)

以下内容摘自：http://www.djangoproject.com/documentation/0.96/templates/

The Django template language: For template authors

This document describes Django version 0.96. For current documentation, go here.

Django's template language is designed to strike a balance between power and ease. It's designed to feel comfortable to those used to working with HTML. If you have any exposure to other text-based template languages, such as Smarty or CheetahTemplate, you should feel right at home with Django's templates.

Templates

A template is simply a text file. It can generate any text-based format (HTML, XML, CSV, etc.).

A template contains variables, which get replaced with values when the template is evaluated, and tags, which control the logic of the template.

Below is a minimal template that illustrates a few basics. Each element will be explained later in this document.:

{% extends "base_generic.html" %}

{% block title %}{{ section.title }}{% endblock %}

{% block content %}

<h1>{{ section.title }}</h1>

{% for story in story_list %}

<h2>

</a>

</h2>

<p>{{ story.tease|truncatewords:"100" }}</p>

{% endfor %}

{% endblock %}

Philosophy

Why use a text-based template instead of an XML-based one (like Zope's TAL)? We wanted Django's template language to be usable for more than just XML/HTML templates. At World Online, we use it for e-mails, JavaScript and CSV. You can use the template language for any text-based format.

Oh, and one more thing: Making humans edit XML is sadistic!

Variables

Variables look like this: {{ variable }}. When the template engine encounters a variable, it evaluates that variable and replaces it with the result.

Use a dot (.) to access attributes of a variable.

Behind the scenes

Technically, when the template system encounters a dot, it tries the following lookups, in this order:

Dictionary lookup
Attribute lookup
Method call
List-index lookup

In the above example, {{ section.title }} will be replaced with the title attribute of the section object.

If you use a variable that doesn't exist, the template system will insert the value of the TEMPLATE_STRING_IF_INVALID setting, which is set to '' (the empty string) by default.

See Using the built-in reference, below, for help on finding what variables are available in a given template.

Filters

You can modify variables for display by using filters.

Filters look like this: {{ name|lower }}. This displays the value of the {{ name }} variable after being filtered through the lowerfilter, which converts text to lowercase. Use a pipe (|) to apply a filter.

Filters can be "chained." The output of one filter is applied to the next. {{ text|escape|linebreaks }} is a common idiom for escaping text contents, then converting line breaks to <p> tags.

Some filters take arguments. A filter argument looks like this: {{ bio|truncatewords:"30" }}. This will display the first 30 words of the bio variable. Filter arguments always are in double quotes.

The Built-in filter reference below describes all the built-in filters.

Tags

Tags look like this: {% tag %}. Tags are more complex than variables: Some create text in the output, some control flow by performing loops or logic, and some load external information into the template to be used by later variables.

Some tags require beginning and ending tags (i.e. {% tag %} ... tag contents ... {% endtag %}). The Built-in tag reference below describes all the built-in tags. You can create your own tags, if you know how to write Python code.

Comments

To comment-out part of a template, use the comment syntax: {# #}.

For example, this template would render as 'hello':

{# greeting #}hello

A comment can contain any template code, invalid or not. For example:

{# {% if foo %}bar{% else %} #}

Template inheritance

The most powerful — and thus the most complex — part of Django's template engine is template inheritance. Template inheritance allows you to build a base "skeleton" template that contains all the common elements of your site and definesblocks that child templates can override.

It's easiest to understand template inheritance by starting with an example:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>{% block title %}My amazing site{% endblock %}</title>

</head>

<body>

{% block sidebar %}

<ul>

</ul>

{% endblock %}

</div>

{% block content %}{% endblock %}

</div>

</body>

</html>

This template, which we'll call base.html, defines a simple HTML skeleton document that you might use for a simple two-column page. It's the job of "child" templates to fill the empty blocks with content.

In this example, the {% block %} tag defines three blocks that child templates can fill in. All the block tag does is to tell the template engine that a child template may override those portions of the template.

A child template might look like this:

{% extends "base.html" %}

{% block title %}My amazing blog{% endblock %}

{% block content %}

{% for entry in blog_entries %}

<h2>{{ entry.title }}</h2>

<p>{{ entry.body }}</p>

{% endfor %}

{% endblock %}

The {% extends %} tag is the key here. It tells the template engine that this template "extends" another template. When the template system evaluates this template, first it locates the parent — in this case, "base.html".

At that point, the template engine will notice the three {% block %} tags in base.html and replace those blocks with the contents of the child template. Depending on the value of blog_entries, the output might look like:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>My amazing blog</title>

</head>

<body>

<ul>

</ul>

</div>

<h2>Entry one</h2>

<p>This is my first entry.</p>

<h2>Entry two</h2>

<p>This is my second entry.</p>

</div>

</body>

</html>

Note that since the child template didn't define the sidebar block, the value from the parent template is used instead. Content within a {% block %} tag in a parent template is always used as a fallback.

You can use as many levels of inheritance as needed. One common way of using inheritance is the following three-level approach:

Create a base.html template that holds the main look-and-feel of your site.
Create a base_SECTIONNAME.html template for each "section" of your site. For example, base_news.html, base_sports.html. These templates all extend base.html and include section-specific styles/design.
Create individual templates for each type of page, such as a news article or blog entry. These templates extend the appropriate section template.

This approach maximizes code reuse and makes it easy to add items to shared content areas, such as section-wide navigation.

Here are some tips for working with inheritance:

If you use {% extends %} in a template, it must be the first template tag in that template. Template inheritance won't work, otherwise.
More {% block %} tags in your base templates are better. Remember, child templates don't have to define all parent blocks, so you can fill in reasonable defaults in a number of blocks, then only define the ones you need later. It's better to have more hooks than fewer hooks.
If you find yourself duplicating content in a number of templates, it probably means you should move that content to a{% block %} in a parent template.
If you need to get the content of the block from the parent template, the {{ block.super }} variable will do the trick. This is useful if you want to add to the contents of a parent block instead of completely overriding it.
For extra readability, you can optionally give a name to your {% endblock %} tag. For example:
{% block content %}
...
{% endblock content %}

In larger templates, this technique helps you see which {% block %} tags are being closed.

Finally, note that you can't define multiple {% block %} tags with the same name in the same template. This limitation exists because a block tag works in "both" directions. That is, a block tag doesn't just provide a hole to fill — it also defines the content that fills the hole in the parent. If there were two similarly-named {% block %} tags in a template, that template's parent wouldn't know which one of the blocks' content to use.

Using the built-in reference

Django's admin interface includes a complete reference of all template tags and filters available for a given site. To see it, go to your admin interface and click the "Documentation" link in the upper right of the page.

The reference is divided into 4 sections: tags, filters, models, and views.

The tags and filters sections describe all the built-in tags (in fact, the tag and filter references below come directly from those pages) as well as any custom tag or filter libraries available.

The views page is the most valuable. Each URL in your site has a separate entry here, and clicking on a URL will show you:

The name of the view function that generates that view.
A short description of what the view does.
The context, or a list of variables available in the view's template.
The name of the template or templates that are used for that view.

Each view documentation page also has a bookmarklet that you can use to jump from any page to the documentation page for that view.

Because Django-powered sites usually use database objects, the models section of the documentation page describes each type of object in the system along with all the fields available on that object.

Taken together, the documentation pages should tell you every tag, filter, variable and object available to you in a given template.

Custom tag and filter libraries

Certain applications provide custom tag and filter libraries. To access them in a template, use the {% load %} tag:

{% load comments %}

{% comment_form for blogs.entries entry.id with is_public yes %}

In the above, the load tag loads the comments tag library, which then makes the comment_form tag available for use. Consult the documentation area in your admin to find the list of custom libraries in your installation.

The {% load %} tag can take multiple library names, separated by spaces. Example:

{% load comments i18n %}

Custom libraries and template inheritance

When you load a custom tag or filter library, the tags/filters are only made available to the current template — not any parent or child templates along the template-inheritance path.

For example, if a template foo.html has {% load comments %}, a child template (e.g., one that has {% extends "foo.html" %}) will nothave access to the comments template tags and filters. The child template is responsible for its own {% load comments %}.

This is a feature for the sake of maintainability and sanity.

Built-in tag and filter reference

For those without an admin site available, reference for the stock tags and filters follows. Because Django is highly customizable, the reference in your admin should be considered the final word on what tags and filters are available, and what they do.

Built-in tag reference

BLOCK

Define a block that can be overridden by child templates. See Template inheritance for more information.

COMMENT

Ignore everything between {% comment %} and {% endcomment %}

CYCLE

Cycle among the given strings each time this tag is encountered.

Within a loop, cycles among the given strings each time through the loop:

{% for o in some_list %}

...

</tr>

{% endfor %}

Outside of a loop, give the values a unique name the first time you call it, then use that name each successive time through:

You can use any number of values, separated by commas. Make sure not to put spaces between the values — only commas.

DEBUG

Output a whole load of debugging information, including the current context and imported modules.

EXTENDS

Signal that this template extends a parent template.

This tag can be used in two ways:

{% extends "base.html" %} (with quotes) uses the literal value "base.html" as the name of the parent template to extend.
{% extends variable %} uses the value of variable. If the variable evaluates to a string, Django will use that string as the name of the parent template. If the variable evaluates to a Template object, Django will use that object as the parent template.

See Template inheritance for more information.

FILTER

Filter the contents of the variable through variable filters.

Filters can also be piped through each other, and they can have arguments — just like in variable syntax.

Sample usage:

{% filter escape|lower %}

This text will be HTML-escaped, and will appear in all lowercase.

{% endfilter %}

FIRSTOF

Outputs the first variable passed that is not False. Outputs nothing if all the passed variables are False.

Sample usage:

{% firstof var1 var2 var3 %}

This is equivalent to:

{% if var1 %}

{% else %}{% if var2 %}

{% else %}{% if var3 %}

{% endif %}{% endif %}{% endif %}

FOR

Loop over each item in an array. For example, to display a list of athletes given athlete_list:

<ul>

{% for athlete in athlete_list %}

<li>{{ athlete.name }}</li>

{% endfor %}

</ul>

You can also loop over a list in reverse by using {% for obj in list reversed %}.

The for loop sets a number of variables available within the loop:

Variable	Description
forloop.counter	The current iteration of the loop (1-indexed)
forloop.counter0	The current iteration of the loop (0-indexed)
forloop.revcounter	The number of iterations from the end of the loop (1-indexed)
forloop.revcounter0	The number of iterations from the end of the loop (0-indexed)
forloop.first	True if this is the first time through the loop
forloop.last	True if this is the last time through the loop
forloop.parentloop	For nested loops, this is the loop "above" the current one

The {% if %} tag evaluates a variable, and if that variable is "true" (i.e. exists, is not empty, and is not a false boolean value) the contents of the block are output:

{% if athlete_list %}

Number of athletes: {{ athlete_list|length }}

{% else %}

No athletes.

{% endif %}

In the above, if athlete_list is not empty, the number of athletes will be displayed by the {{ athlete_list|length }} variable.

As you can see, the if tag can take an optional {% else %} clause that will be displayed if the test fails.

if tags may use and, or or not to test a number of variables or to negate a given variable:

{% if athlete_list and coach_list %}

Both athletes and coaches are available.

{% endif %}

{% if not athlete_list %}

There are no athletes.

{% endif %}

{% if athlete_list or coach_list %}

There are some athletes or some coaches.

{% endif %}

{% if not athlete_list or coach_list %}

There are no athletes or there are some coaches (OK, so

writing English translations of boolean logic sounds

stupid; it's not our fault).

{% endif %}

{% if athlete_list and not coach_list %}

There are some athletes and absolutely no coaches.

{% endif %}

if tags don't allow and and or clauses within the same tag, because the order of logic would be ambiguous. For example, this is invalid:

{% if athlete_list and coach_list or cheerleader_list %}

If you need to combine and and or to do advanced logic, just use nested if tags. For example:

{% if athlete_list %}

{% if coach_list or cheerleader_list %}

We have athletes, and either coaches or cheerleaders!

{% endif %}

Multiple uses of the same logical operator are fine, as long as you use the same operator. For example, this is valid:

{% if athlete_list or coach_list or parent_list or teacher_list %}

IFCHANGED

Check if a value has changed from the last iteration of a loop.

The 'ifchanged' block tag is used within a loop. It has two possible uses.

Checks its own rendered contents against its previous state and only displays the content if it has changed. For example, this displays a list of days, only displaying the month if it changes:
<h1>Archive for {{ year }}</h1>
{% for date in days %}
{% ifchanged %}<h3>{{ date|date:"F" }}</h3>{% endifchanged %}
<a href="{{ date|date:"M/d"|lower }}/">{{ date|date:"j" }}</a>
{% endfor %}
If given a variable, check whether that variable has changed. For example, the following shows the date every time it changes, but only shows the hour if both the hour and the date has changed:
{% for date in days %}
{% ifchanged date.date %} {{ date.date }} {% endifchanged %}
{% ifchanged date.hour date.date %}
{{ date.hour }}
{% endifchanged %}
{% endfor %}

IFEQUAL

Output the contents of the block if the two arguments equal each other.

Example:

{% ifequal user.id comment.user_id %}

...

{% endifequal %}

As in the {% if %} tag, an {% else %} clause is optional.

The arguments can be hard-coded strings, so the following is valid:

{% ifequal user.username "adrian" %}

...

{% endifequal %}

It is only possible to compare an argument to template variables or strings. You cannot check for equality with Python objects such as True or False. If you need to test if something is true or false, use the if tag instead.

IFNOTEQUAL

Just like ifequal, except it tests that the two arguments are not equal.

INCLUDE

Loads a template and renders it with the current context. This is a way of "including" other templates within a template.

The template name can either be a variable or a hard-coded (quoted) string, in either single or double quotes.

This example includes the contents of the template "foo/bar.html":

{% include "foo/bar.html" %}

This example includes the contents of the template whose name is contained in the variable template_name:

{% include template_name %}

An included template is rendered with the context of the template that's including it. This example produces the output"Hello, John":

Context: variable person is set to "john".
Template:
{% include "name_snippet.html" %}
The name_snippet.html template:
Hello, {{ person }}

See also: {% include %}.

TEMPLATETAG

Output one of the syntax characters used to compose template tags.

Since the template system has no concept of "escaping", to display one of the bits used in template tags, you must use the{% templatetag %} tag.

The argument tells which template bit to output:

Argument	Outputs
openblock	{%
closeblock	%}
openvariable	{{
closevariable	}}
openbrace	{
closebrace	}
opencomment	{#
closecomment	#}

URL

Note that the syntax for this tag may change in the future, as we make it more robust.

Returns an absolute URL (i.e., a URL without the domain name) matching a given view function and optional parameters. This is a way to output links without violating the DRY principle by having to hard-code URLs in your templates:

{% url path.to.some_view arg1,arg2,name1=value1 %}

The first argument is a path to a view function in the format package.package.module.function. Additional arguments are optional and should be comma-separated values that will be used as positional and keyword arguments in the URL. All arguments required by the URLconf should be present.

For example, suppose you have a view, app_name.client, whose URLconf takes a client ID. The URLconf line might look like this:

('^client/(\d+)/$', 'app_name.client')

If this app's URLconf is included into the project's URLconf under a path such as this:

('^clients/', include('project_name.app_name.urls'))

…then, in a template, you can create a link to this view like this:

{% url app_name.client client.id %}

The template tag will output the string /clients/client/123/.

WIDTHRATIO

For creating bar charts and such, this tag calculates the ratio of a given value to a maximum value, and then applies that ratio to a constant.

For example:

Above, if this_value is 175 and max_value is 200, the the image in the above example will be 88 pixels wide (because 175/200 = .875; .875 * 100 = 87.5 which is rounded up to 88).

Built-in filter reference

ADD

Adds the arg to the value.

ADDSLASHES

Adds slashes. Useful for passing strings to JavaScript, for example.

CAPFIRST

Capitalizes the first character of the value.

CENTER

Centers the value in a field of a given width.

CUT

Removes all values of arg from the given string.

DATE

Formats a date according to the given format (same as the now tag).

DEFAULT

If value is unavailable, use given default.

DEFAULT_IF_NONE

If value is None, use given default.

DICTSORT

Takes a list of dicts, returns that list sorted by the property given in the argument.

DICTSORTREVERSED

Takes a list of dicts, returns that list sorted in reverse order by the property given in the argument.

DIVISIBLEBY

Returns true if the value is divisible by the argument.

ESCAPE

Escapes a string's HTML. Specifically, it makes these replacements:

"&" to "&"
< to "<"
> to ">"
'"' (double quote) to '"'
"'" (single quote) to '''

FILESIZEFORMAT

Format the value like a 'human-readable' file size (i.e. '13 KB', '4.1 MB', '102 bytes', etc).

FIRST

Returns the first item in a list.

FIX_AMPERSANDS

Replaces ampersands with & entities.

FLOATFORMAT

When used without an argument, rounds a floating-point number to one decimal place — but only if there's a decimal part to be displayed. For example:

36.123 gets converted to 36.1
36.15 gets converted to 36.2
36 gets converted to 36

If used with a numeric integer argument, floatformat rounds a number to that many decimal places. For example:

36.1234 with floatformat:3 gets converted to 36.123
36 with floatformat:4 gets converted to 36.0000

If the argument passed to floatformat is negative, it will round a number to that many decimal places — but only if there's a decimal part to be displayed. For example:

36.1234 with floatformat:-3 gets converted to 36.123
36 with floatformat:-4 gets converted to 36

Using floatformat with no argument is equivalent to using floatformat with an argument of -1.

GET_DIGIT

Given a whole number, returns the requested digit of it, where 1 is the right-most digit, 2 is the second-right-most digit, etc. Returns the original value for invalid input (if input or argument is not an integer, or if argument is less than 1). Otherwise, output is always an integer.

JOIN

Joins a list with a string, like Python's str.join(list).

LENGTH

Returns the length of the value. Useful for lists.

LENGTH_IS

Returns a boolean of whether the value's length is the argument.

LINEBREAKS

Converts newlines into <p> and <br /> tags.

LINEBREAKSBR

Converts newlines into <br /> tags.

LINENUMBERS

Displays text with line numbers.

LJUST

Left-aligns the value in a field of a given width.

Argument: field size

LOWER

Converts a string into all lowercase.

MAKE_LIST

Returns the value turned into a list. For an integer, it's a list of digits. For a string, it's a list of characters.

PHONE2NUMERIC

Converts a phone number (possibly containing letters) to its numerical equivalent. For example, '800-COLLECT' will be converted to '800-2655328'.

The input doesn't have to be a valid phone number. This will happily convert any string.

PLURALIZE

Returns a plural suffix if the value is not 1. By default, this suffix is 's'.

Example:

You have {{ num_messages }} message{{ num_messages|pluralize }}.

For words that require a suffix other than 's', you can provide an alternate suffix as a parameter to the filter.

Example:

You have {{ num_walruses }} walrus{{ num_walrus|pluralize:"es" }}.

For words that don't pluralize by simple suffix, you can specify both a singular and plural suffix, separated by a comma.

Example:

You have {{ num_cherries }} cherr{{ num_cherries|pluralize:"y,ies" }}.

PPRINT

A wrapper around pprint.pprint — for debugging, really.

RANDOM

Returns a random item from the list.

REMOVETAGS

Removes a space separated list of [X]HTML tags from the output.

RJUST

Right-aligns the value in a field of a given width.

Argument: field size

SLICE

Returns a slice of the list.

Uses the same syntax as Python's list slicing. See http://diveintopython.org/native_data_types/lists.html#odbchelper.list.slice for an introduction.

Example: {{ some_list|slice:":2" }}

SLUGIFY

Converts to lowercase, removes non-word characters (alphanumerics and underscores) and converts spaces to hyphens. Also strips leading and trailing whitespace.

STRINGFORMAT

Formats the variable according to the argument, a string formatting specifier. This specifier uses Python string formating syntax, with the exception that the leading "%" is dropped.

See http://docs.python.org/lib/typesseq-strings.html for documentation of Python string formatting

STRIPTAGS

Strips all [X]HTML tags.

TIME

Formats a time according to the given format (same as the now tag).

TIMESINCE

Formats a date as the time since that date (i.e. "4 days, 6 hours").

Takes an optional argument that is a variable containing the date to use as the comparison point (without the argument, the comparison point is now). For example, if blog_date is a date instance representing midnight on 1 June 2006, and comment_dateis a date instance for 08:00 on 1 June 2006, then {{ comment_date|timesince:blog_date }} would return "8 hours".

TIMEUNTIL

Similar to timesince, except that it measures the time from now until the given date or datetime. For example, if today is 1 June 2006 and conference_date is a date instance holding 29 June 2006, then {{ conference_date|timeuntil }} will return "28 days".

Takes an optional argument that is a variable containing the date to use as the comparison point (instead of now). Iffrom_date contains 22 June 2006, then {{ conference_date|timeuntil:from_date }} will return "7 days".

TITLE

Converts a string into titlecase.

TRUNCATEWORDS

Truncates a string after a certain number of words.

Argument: Number of words to truncate after

TRUNCATEWORDS_HTML

Similar to truncatewords, except that it is aware of HTML tags. Any tags that are opened in the string and not closed before the truncation point, are closed immediately after the truncation.

This is less efficient than truncatewords, so should only be used when it is being passed HTML text.

UNORDERED_LIST

Recursively takes a self-nested list and returns an HTML unordered list — WITHOUT opening and closing <ul> tags.

The list is assumed to be in the proper format. For example, if var contains['States', [['Kansas', [['Lawrence', []], ['Topeka', []]]], ['Illinois', []]]], then {{ var|unordered_list }} would return:

<li>States

<ul>

<li>Kansas

<ul>

<li>Lawrence</li>

<li>Topeka</li>

</ul>

</li>

<li>Illinois</li>

</ul>

</li>

UPPER

Converts a string into all uppercase.

URLENCODE

Escapes a value for use in a URL.

URLIZE

Converts URLs in plain text into clickable links.

URLIZETRUNC

Converts URLs into clickable links, truncating URLs to the given character limit.

Argument: Length to truncate URLs to

WORDCOUNT

Returns the number of words.

WORDWRAP

Wraps words at specified line length.

Argument: number of characters at which to wrap the text

YESNO

Given a string mapping values for true, false and (optionally) None, returns one of those strings according to the value:

Value	Argument	Outputs
True	"yeah,no,maybe"	yeah
False	"yeah,no,maybe"	no
None	"yeah,no,maybe"	maybe
None	"yeah,no"	"no" (converts None to False if no mapping for None is given)

Other tags and filter libraries

Django comes with a couple of other template-tag libraries that you have to enable explicitly in your INSTALLED_APPS setting and enable in your template with the {% load %} tag.

django.contrib.humanize

A set of Django template filters useful for adding a "human touch" to data. See the humanize documentation.

django.contrib.markup

A collection of template filters that implement these common markup languages:

Textile
Markdown
ReST (ReStructured Text)

posted on 2009-10-15 16:56 rain.j 阅读(482) 评论(0) 编辑收藏举报

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Format character	Description	Example output
a	'a.m.' or 'p.m.' (Note that this is slightly different than PHP's output, because this includes periods to match Associated Press style.)	'a.m.'
A	'AM' or 'PM'.	'AM'
b	Month, textual, 3 letters, lowercase.	'jan'
B	Not implemented.
d	Day of the month, 2 digits with leading zeros.	'01' to '31'
D	Day of the week, textual, 3 letters.	'Fri'
f	Time, in 12-hour hours and minutes, with minutes left off if they're zero. Proprietary extension.	'1', '1:30'
F	Month, textual, long.	'January'
g	Hour, 12-hour format without leading zeros.	'1' to '12'
G	Hour, 24-hour format without leading zeros.	'0' to '23'
h	Hour, 12-hour format.	'01' to '12'
H	Hour, 24-hour format.	'00' to '23'
i	Minutes.	'00' to '59'
I	Not implemented.
j	Day of the month without leading zeros.	'1' to '31'
l	Day of the week, textual, long.	'Friday'
L	Boolean for whether it's a leap year.	True or False
m	Month, 2 digits with leading zeros.	'01' to '12'
M	Month, textual, 3 letters.	'Jan'
n	Month without leading zeros.	'1' to '12'
N	Month abbreviation in Associated Press style. Proprietary extension.	'Jan.', 'Feb.', 'March', 'May'
O	Difference to Greenwich time in hours.	'+0200'
P	Time, in 12-hour hours, minutes and 'a.m.'/'p.m.', with minutes left off if they're zero and the special-case strings 'midnight' and 'noon' if appropriate. Proprietary extension.	'1 a.m.', '1:30 p.m.', 'midnight', 'noon', '12:30 p.m.'
r	RFC 822 formatted date.	'Thu, 21 Dec 2000 16:01:07 +0200'
s	Seconds, 2 digits with leading zeros.	'00' to '59'
S	English ordinal suffix for day of the month, 2 characters.	'st', 'nd', 'rd' or 'th'
t	Number of days in the given month.	28 to 31
T	Time zone of this machine.	'EST', 'MDT'
U	Not implemented.
w	Day of the week, digits without leading zeros.	'0' (Sunday) to '6' (Saturday)
W	ISO-8601 week number of year, with weeks starting on Monday.	1, 23
y	Year, 2 digits.	'99'
Y	Year, 4 digits.	'1999'
z	Day of the year.	0 to 365
Z	Time zone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.	-43200 to 43200