Tagged templates for Python
Project description
tagged
![PyPI](https://pypi-camo.freetls.fastly.net/2e62bc311a6d9ff7ee2e6f18b97f7ae3cb0eb691/68747470733a2f2f696d672e736869656c64732e696f2f707970692f762f7461676765642e7376673f636f6c6f723d626c7565)
A Python version of JavaScript's tagged templates, mixed with Python 3's f-strings.
For a more involved example how this package can be used in practice, see htm.py that implements JSX-like syntax in plain Python.
Installation
$ pip3 install tagged
Usage
This package defines tag
, a decorator for creating new tags. Let's define a simple one:
from tagged import tag
@tag
def t(strings, values):
return strings, values
Now t
can be called with a template string that can contain any Python 3 expression between {
and }
. The "static" parts of the string are listed in strings
and the evaluated expressions are listed in values
.
strings, values = t("1 + {2} equals {1 + 2}")
# strings == ('1 + ', ' equals ', '')
# values == (2, 3)
Because the expressions are evaluated in the current context they can refer to local variables:
a = [1, 2, 3]
strings, values = t("the sum of {a} is {sum(a)}")
# strings == ('the sum of ', ' is ', '')
# values == ([1, 2, 3], 6)
Double curly brackets are interpreted as a single textual curly bracket:
strings, values = t("Inline a set between {{ and }} like this: {({1, 2, 3})}")
# strings == ('Inline a set between { and } like this: ', '')
# values == ({1, 2, 3},)
rexample
Let's define a custom tag rex
that allows composing regular expressions from strings and other regular expressions.
import re
from tagged import tag
@tag
def rex(strings, values):
pattern = strings[0]
for value, string in zip(values, strings[1:]):
if isinstance(value, re.Pattern):
value = value.pattern
elif isinstance(value, str):
value = re.escape(value)
else:
raise TypeError("expected re.Pattern or str")
pattern += "(?:" + value + ")" + string
return re.compile(pattern)
greeting = re.compile("Hello|Hi|Greetings")
name = "Python 3.7"
rex("{greeting}, {name}!")
# re.compile('(?:Hello|Hi|Greetings), (?:Python\\ 3\\.7)!')
Development
Running Tests
$ python3 -m unittest discover -s tests
License
This library is licensed under the MIT license. See ./LICENSE.
Project details
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