I want to create an engine in python that can replace tags in a template file with objects from json? I've loooked at python based engines that use regex but they are overly complicated and I am a little confused as to how to start an go about it. Any code to start would help
Sample json file
{
"webbpage": {
"title": "Stackoverflow"
},
"Songs": {
"name": "Mr Crowley"
},
"CoverArtists": [
{ "name": "Ozzy", "nicknames": ["Ozzman","Ozzster"] },
{ "name": "Slipknot", "nicknames": ["Slip"] }
]
}
Sample template file
<html>
<head>
<title><%% webbpage.title %%></title>
</head>
<body>
<h1><%% Songs.name %%></h1>
<%% EACH CoverArtists artist %%>
<%% artist.name %%>
<%% EACH CoverArtists.nicknames nickname %%>
<p><%% nickname %%></p>
<%% END %%>
<%% END %%>
</body>
</html>
Basically variables are identified between <%% and %%> and loops are identifed between <%% EACH .. %%> AND <%% END %%> and basically output html
Check out Alex Mitchells blog on templating (python based), it's extremely helpful, and the related GIT here
Basically,
Take input files on command line
Parse template file - build Abstract Syntax tree to parse easily. Create a node base type, and then for each new type implement a concrete class
Build stack to keep track of loops, pop when loops close, look for errors of missing loop ends
Parse json file, build dictionary of objects, map AST entries and replace in html
Write output to file.
I have a version of this based on Alex mitchells engine here, where I've fixed some issues with the original one( and put it in some code of my own) and will be trying to get rid of the reg exp based matching and put in contextual matching, because regular expressions dont work too well on large complex HTML data.
So basically you need to identify tokens within <%% and %%>. This step can be done with a regular expression, e.g. :
>>> import re
>>> t='<h1><%% Songs.name %%></h1>'
>>> re.search(r'<%%(.+?)%%>', t).groups()
(' Songs.name ',)
Parsing the code that this gives is quite a complicated task, and you might find some help in shlex or tokenizer. Even if you need to use regular expressions for the entire project, I suggest you take a look at these, and examples from other languages, to understand how a syntax parser works.
Once you've parsed the language, the next step is to replace the tokens with values from json. The best way would be to first load the data into python dicts, and then write a renderer to insert the data into the html.
Even if you can't use them, you should still have a look at some templating engines such as jinja or chameleon and study their source code to get an idea of how such a project is put together.
Related
I try to get string translations working in Pyramid with ZPT templates. I followed the Pyramid guide on internationalization and localization, i.e. http://docs.pylonsproject.org/projects/pyramid/en/latest/narr/i18n.html#chameleon-template-support-for-translation-strings.
However, when I add the line
<span>${some_translation_string}</span>
to my .pt template file I just get an assertion message from waitress:
NameError: some_translation_string
When I translate the string some_translation_string outside the ZPT templates (i.e. in the Python code of the view) it translates correctly. Thus, I think to have a valid compiled message catalog in place (though created manually due to missing Python3 support of babel/lingua).
I guess I misunderstand the way to insert localized strings in ZPT templates in general. It probably cannot be the same as for referencing variables?
As I understand now, translations within the ZPT template should look like this:
<span i18n:translate="">some_translation_string</h1>
If you omit the string identifier in i18n:translate the string itself is used for this.
Also you must add add the domain name in the template header, e.g.:
<html lang="en"
xmlns:tal="http://xml.zope.org/namespaces/tal"
xmlns:metal="http://xml.zope.org/namespaces/metal"
xmlns:i18n="http://xml.zope.org/namespaces/i18n"
i18n:domain="my_domain">
This information seems to be missing in the referenced Pyramid documentation.
For reference, to do translations for messages in your JavaScript code, I found this way handy:
In your view, add a TranslationStringFactory instance to the template parameters:
from translationstring import TranslationStringFactory
#view_config(route_name='site', renderer='templates/site.pt')
def form(request):
...
return {'_': TranslationStringFactory('yourapp')}
Then in the template you can write:
<script type="text/javascript">
...
yourapp.i18n['error'] = '${_('Error')}';
yourapp.i18n['warning'] = '${_('Warning')}';
</script>
Possibly i am overlooking an obvious solution or thinking the wrong way...
I have a limited amount of text, words in a database, that I want to display translated to users in a flask/jinja/babel webapp. eg. "running" is a possible value of an "activity" column and that should be "laufen" for my german users.
Words in templates and code are extracted and put into the catalog, but how do i get additional words into the catalog? Is there a simple text file extractor?
The only thing i could think of is, just create a .py file and put lots of _('...') lines in them, but that feels just wrong... is it?
I created a messages.txt with my "words" like gettext function calls:
_('cycling')
_('running')
and added it to my babel.cfg as python source:
[python: messages.txt]
plain, simple, stupid, but works.
First, start with http://flask.pocoo.org/snippets/4/.
Secondly, you need to store these 'limited' values as integers or enums in database and then create the lookup table for all these enums in code (so Babel knows about them):
i18n_val = {0: _('running'), ...}
# Or multi-level dict with different categories:
i18n_all = {
'activity': {
0: _('running'), ...
'foo': {
0: _('bar..'), ...
}
}
And accessing the translated string from template is now as simple as:
{{ i18n_val[obj.activity] }}
{{ i18n_all['activity'][obj.activity] }}
In order to make the i18n_val and i18n_all variables available for all the templates, just register them with context processors.
I am new to both Python (and django) - but not to programming.
I am having no end of problems with identation in my view. I am trying to generate my html dynamically, so that means a lot of string manipulation. Obviously - I cant have my entire HTML page in one line - so what is required in order to be able to dynamically build an html string, i.e. mixing strings and other variables?
For example, using PHP, the following trivial example demonstrates generating an HTML doc containing a table
<?php
$output = '<html><head><title>Getting worked up over Python indentations</title></head><body>';
output .= '<table><tbody>'
for($i=0; $i< 10; $i++){
output .= '<tr class="'.(($i%2) ? 'even' : 'odd').'"><td>Row: '.$i;
}
$output .= '</tbody></table></body></html>'
echo $output;
I am trying to do something similar in Python (in my views.py), and I get errors like:
EOL while scanning string literal (views.py, line 21)
When I put everything in a single line, it gets rid of the error.
Could someone show how the little php script above will be written in python?, so I can use that as a template to fix my view.
[Edit]
My python code looks something like this:
def just_frigging_doit(request):
html = '<html>
<head><title>What the funk<title></head>
<body>'
# try to start builing dynamic HTML from this point onward...
# but server barfs even further up, on the html var declaration line.
[Edit2]
I have added triple quotes like suggested by Ned and S.Lott, and that works fine if I want to print out static text. If I want to create dynamic html (for example a row number), I get an exception - cannot concatenate 'str' and 'int' objects.
I am trying to generate my html dynamically, so that means a lot of string manipulation.
Don't do this.
Use Django's templates. They work really, really well. If you can't figure out how to apply them, do this. Ask a question showing what you want to do. Don't ask how to make dynamic HTML. Ask about how to create whatever page feature you're trying to create. 80% of the time, a simple {%if%} or {%for%} does everything you need. The rest of the time you need to know how filters and the built-in tags work.
Use string.Template if you must fall back to "dynamic" HTML. http://docs.python.org/library/string.html#template-strings Once you try this, you'll find Django's is better.
Do not do string manipulation to create HTML.
cannot concatenate 'str' and 'int' objects.
Correct. You cannot.
You have three choices.
Convert the int to a string. Use the str() function. This doesn't scale well. You have lots of ad-hoc conversions and stuff. Unpleasant.
Use the format() method of a string to insert values into the string. This is slightly better than complex string manipulation. After doing this for a while, you figure out why templates are a good idea.
Use a template. You can try string.Template. After a while, you figure out why Django's are a good idea.
my_template.html
<html><head><title>Getting worked up over Python indentations</title></head><body>
<table><tbody>
{%for object in objects%}
<tr class="{%cycle 'even' 'odd'%}"><td>Row: {{object}}</td></tr>
{%endfor%}
</tbody></table></body></html>
views.py
def myview( request ):
render_to_response( 'my_template.html',
{ 'objects':range(10) }
)
I think that's all you'd need for a mockup.
In Python, a string can span lines if you use triple-quoting:
"""
This is a
multiline
string
"""
You probably want to use Django templates to create your HTML. Read a Django tutorial to see how it's done.
Python is strongly typed, meaning it won't automatically convert types for you to make your expressions work out, the way PHP will. So you can't concatenate strings and numbers like this: "hello" + num.
I am looking for an easily implemented HTML generator for Python. I found HTML.py, but there is no way to add CSS elements (id, class) for table.
Dominate is an HTML generation library that lets you easily create tags. In dominate, python reserved words are prefixed with an underscore, so it would look like this:
from dominate.tags import *
t = div(table(_id="the_table"), _class="tbl")
print(t)
<div class="tbl">
<table id="the_table"></table>
</div>
Disclaimer: I am the author of dominate
If you want programmatic generation rather than templating, Karrigell's HTMLTags module is one possibility; it can include e.g. the class attribute (which would be a reserved word in Python) by the trick of uppercasing its initial, i.e., quoting the doc URL I just gave:
Attributes with the same name as
Python keywords (class, type) must be
capitalized :
print DIV('bar', Class="title") ==> <DIV class="title">bar</DIV>
HTML Generation is usually done with one of the infinite amounts of HTML templating languages available for Python. Personally I like Templess, but Genshi is probably the most popular. There are infinite amounts of them, there is a list which is highly likely to be incomplete.
Otherwise you might want to use lxml, where you can generate it in a more programmatically XML-ish way. Although I have a hard time seeing the benefit.
There's the venerable HTMLGen by Robin Friedrich, which is hard to find but still available here (dated 2001, but HTML hasn't changed much since then ;-). There's also xist. Of course nowadays HTML generation, as Lennart points out, is generally better done using templating systems such as Jinja or Mako.
This is one ultra-simple HTML generator I have written. I use it build-time to generate html. If one is generating html pages run-time then there are better options available
Here is the link
http://pypi.python.org/pypi/sphc
And a quick example
>> import sphw
>> tf = sphw.TagFactory()
>>> div = tf.DIV("Some Text here.", Class='content', id='foo')
>>> print(div)
<DIV Class="content", id="foo">Some Text here.</DIV>
Actually you can add any attribute such as id and class to objects in HTML.py (http://www.decalage.info/python/html).
attribs is an optional parameter of Table, TableRow and TableCell classes. It is a dictionary of additional attributes you would like to set. For example, the following code sets id and class for a table:
import HTML
table_data = [
['Last name', 'First name', 'Age'],
['Smith', 'John', 30],
['Carpenter', 'Jack', 47],
['Johnson', 'Paul', 62],
]
htmlcode = HTML.table(table_data,
attribs={'id':'table1', 'class':'myclass'})
print htmlcode
The same parameter can be used with TableRow and TableCell objects to format rows and cells. It does not exist for columns yet, but should be easy to implement if needed.
Ok, here's another html generator, or I prefer to think of it as a compiler.
https://pypi.python.org/pypi/python-html-compiler
This is a set of base classes that can be used to define tags and attributes. Thus a tag class has attributes and children. Children are themselves Tag classes that have attributes and children etc etc. Also you can set parameters that start with your root class and work up the various branches.
This will allow you to define all the tag classes you want thus be able to create customised classes and implement any tags or attributes you want.
Just started on this, so if anybody wants to test :)
Html generation or any text generatio,jinja is a powerful template engine.
You might be interested in some of the Python HAML implementations. HAML is like HTML shorthand and only takes a few minutes to learn. There's a CSS version called SASS too.
http://haml.hamptoncatlin.com/
"Is there a HAML implementation for use with Python and Django" talks about Python and HAML a bit more.
I'm using HAML as much as possible when I'm programming in Ruby. And, as a footnote, there's also been some work getting modules for Perl which work with the nice MVC Mojolicious:
http://metacpan.org/pod/Text::Haml
I recently discovered the genshi.builder module. It reminds me of Divmod Nevow's Stan module. How would one use genshi.builder.tag to build an HTML document with a particular doctype? Or is this even a good thing to do? If not, what is the right way?
It's not possible to build an entire page using just genshi.builder.tag -- you would need to perform some surgery on the resulting stream to insert the doctype. Besides, the resulting code would look horrific. The recommended way to use Genshi is to use a separate template file, generate a stream from it, and then render that stream to the output type you want.
genshi.builder.tag is mostly useful for when you need to generate simple markup from within Python, such as when you're building a form or doing some sort of logic-heavy modification of the output.
See documentation for:
Creating and using templates
The XML-based template language
genshi.builder API docs
If you really want to generate a full document using only builder.tag, this (completely untested) code could be a good starting point:
from itertools import chain
from genshi.core import DOCTYPE, Stream
from genshi.output import DocType
from genshi.builder import tag as t
# Build the page using `genshi.builder.tag`
page = t.html (t.head (t.title ("Hello world!")), t.body (t.div ("Body text")))
# Convert the page element into a stream
stream = page.generate ()
# Chain the page stream with a stream containing only an HTML4 doctype declaration
stream = Stream (chain ([(DOCTYPE, DocType.get ('html4'), None)], stream))
# Convert the stream to text using the "html" renderer (could also be xml, xhtml, text, etc)
text = stream.render ('html')
The resulting page will have no whitespace in it -- it'll look normal, but you'll have a hard time reading the source code because it will be entirely on one line. Implementing appropriate filters to add whitespace is left as an exercise to the reader.
Genshi.builder is for "programmatically generating markup streams"[1]. I believe the purpose of it is as a backend for the templating language. You're probably looking for the templating language for generating a whole page.
You can, however do the following:
>>> import genshi.output
>>> genshi.output.DocType('html')
('html', '-//W3C//DTD HTML 4.01//EN', 'http://www.w3.org/TR/html4/strict.dtd')
See other Doctypes here: http://genshi.edgewall.org/wiki/ApiDocs/genshi.output#genshi.output:DocType
[1] genshi.builder.__doc__