Format python data structures in HTML no dependencies

Question

My poorly written tests suggests that the module works as intended. I fear this is to good to be true. I don't known how to write unit tests for this. I'm new to writing tests and I think this module would be hard for a unit test master to test.

#-*-coding:utf8;-*-
#qpy:3
#qpy:console
SINGLETONS = [
 'area',
 'base',
 'br',
 'col',
 'command',
 'embed',
 'hr',
 'img',
 'input',
 'keygen',
 'link',
 'meta',
 'param',
 'source',
 'track',
 'wbr'
]
# Constants.
SP = ' '
EMPTY = ''
def is_singleton(tag):
 return tag in SINGLETONS
def not_singleton(tag):
 return is_singleton(tag) == False
def html_attributes(**kw):
 # 'attrs' is the elements attributes.
 # Iterate over the keys and values of the kw dict
 # and transform them into a string of html 
 # attributes. Two html attribute keys are 
 # Python keywords 'class' and 'id' to set
 # the id and class of and element use:
 # cls for class and '_id' for 'id.'
 attrs = EMPTY
 n_attrs = len(kw)
 for key, value in zip(kw.keys(), kw.values()):
 if key == 'cls':
 key = 'class'
 if key == '_id':
 key = 'id'
 if n_attrs > 1:
 attrs += '{}="{}"{}'.format(key, value, SP)
 else:
 attrs += '{}="{}"'.format(key, value)
 return attrs.rstrip(SP)
def tagify(tagname, data=EMPTY, **kw):
 if isinstance(data, str):
 data = data.replace('\n', '<br>')
 attrs = html_attributes(**kw)
 if not attrs:
 opentag = '<{}>'.format(tagname)
 else:
 opentag = '<{}{}{}>'.format(tagname, SP, attrs)
 if not_singleton(tagname):
 closetag = '</{}>'.format(tagname)
 else:
 closetag = None
 if not closetag:
 return '{}'.format(opentag)
 if data:
 return '{}{}{}'.format(opentag, data, closetag)
 else:
 return '{}{}'.format(opentag, closetag)
def tag(tagname, **deco_kw):
 '''
 Decorate a functions output with html by
 passing it through tagify.
 '''
 def deco(func):
 def wraps(*args, **kw):
 content = func(*args, **kw)
 return tagify(tagname, content, **deco_kw)
 return wraps
 return deco
def tests():
 '''
 This is a temporary function for
 testing the module.
 Please dont include this in any reviews.
 '''
 @tag('li', cls='link', _id='list-item')
 def link(name, **kw):
 return tagify('a', name, **kw)
 @tag('article', cls='main', _id='spam')
 def paragraph(content, **kw):
 return tagify('p', content, **kw)
 print(link(__name__, src=__file__))
 print(paragraph(list(range(10)), _id='monty'))
if __name__ == '__main__':
 tests()

test() output

---

<li id="list-item" class="link"><a src="/">__main__</a></li>
<article id="spam" class="main"><p id="monty">[0, 1, 2, 3, 4]</p></article>

• Grajdeanu Alex: Could you please tell us why you can't use any dependency? Or at least Python's builtins?
• Ricky Wilson: @MrGrj Its not that I couldn't use third party modules like lxml or builtins like html.dom. I wanted something simple and pretty.

Answer 1

The better way to do this would be to use html_lib, but short of that, here are a few suggestions.

not_singleton is useless. Just use not singleton.

Use kw.items instead of zip(kw.keys(), kw.values()).

Don't use SP, use ' '.

Answer 2

Styleguide (PEP8)

• avoid useless comments
• you should have two new lines between your methods
• docstrings should be written within triple double-quotes
• after # you should have a space

---

Identity vs equality

There is a simple rule of thumb to tell you when to use == or is.

• == is for value equality. Use it when you would like to know if two objects have the same value.
• is is for reference equality. Use it when you would like to know if two references refer to the same object.

For example:

def not_singleton(tag):
 return is_singleton(tag) == False

Should actually be:

def not_singleton(tag):
 return is_singleton(tag) is False

---

Iterating over keys and values of a dict

Instead of this:

for key, value in zip(kw.keys(), kw.values()):
 ...

You should do this:

for key, value in kw.items():
 ...

To be continued

• Daniel: is_singleton(tag) is False: please, just do not is_singleton(tag)