Common Use Cases¶
tinycss2 has been created for WeasyPrint, and many common use cases can thus be found in its repository.
Parsing Stylesheets¶
Parsing whole stylesheets is done using tinycss2.parse_stylesheet()
and
tinycss2.parse_stylesheet_bytes()
.
When CSS comes as Unicode strings, tinycss2.parse_stylesheet()
is the
function to use. If you know for sure how to decode CSS bytes, or if you want
to parse CSS in Unicode strings, you can safely use this function to get rules
out of CSS text.
tinycss2.parse_stylesheet('body div { width: 50% }')
# [<QualifiedRule … { … }>]
tinycss2.parse_stylesheet()
has two extra parameters: skip_comments
if you do not want to generate comment tokens at the top-level of the
stylesheet, and skip_whitespace
if you want to ignore top-level extra
whitespaces.
In many cases, it is hard to know which charset to use. When downloading
stylesheets from an online HTML document, you may have a BOM, a @charset
rule, a protocol encoding defined by HTTP and an
environment encoding.
tinycss2 provides tinycss2.parse_stylesheet_bytes()
that knows how to
handle these different hints. Use it when your CSS is stored offline or online
in a file, it may solve many decoding problems for you.
with open('file.css', 'rb') as fd:
css = fd.read()
tinycss2.parse_stylesheet_bytes(css)
# [<QualifiedRule … { … }>]
tinycss2.parse_stylesheet_bytes()
allows two extra optional arguments:
protocol_encoding
that may be provided by your network protocol, and
environment_encoding
used as a fallback encoding if the other ones failed.
Parsing Rules¶
Parsing a list of declarations is possible from a list of tokens (given by the
content
attribute of tinycss2.parse_stylesheet()
rules) or from a
string (given by the style
attribute of an HTML element, for example).
The high-level function used to parse declarations is
tinycss2.parse_blocks_contents()
.
rules = tinycss2.parse_stylesheet('body div {width: 50%;height: 50%}')
tinycss2.parse_blocks_contents(rules[0].content)
# [<Declaration width: …>, <Declaration height: …>]
tinycss2.parse_blocks_contents('width: 50%;height: 50%')
# [<Declaration width: …>, <Declaration height: …>]
You can then get the name and value of each declaration:
declarations = tinycss2.parse_blocks_contents('width: 50%;height: 50%')
declarations[0].name, declarations[0].value
# ('width', [<WhitespaceToken>, <PercentageToken 50%>])
This function has the same skip_comments
and skip_whitespace
parameters
as the parse_stylesheet*
functions.
Serializing¶
tinycss2 is also able to generate CSS strings out of abstact Python trees. You
can use tinycss2.ast.Node.serialize()
to generate a CSS string that would
give the same serialization as the original string.
rules = tinycss2.parse_stylesheet('body div { width: 50% }')
rule = rules[0]
print(rule.serialize())
# 'body div { width: 50% }'