future-tstrings

A backport of tstrings to python<3.14

Also serves as a backport of full-syntax fstrings (PEP701-style) to python <3.12.

Does nothing on 3.14 or higher.

Requires python >= 3.8

Installation

pip install future-tstrings

Usage

Include the following magic line at the top of the file (before regular imports)

# future-tstrings

And then write python 3.14 tstring and fstring code as usual!

- example.py

from string.templatelib import Template  # or, future_tstrings.templatelib

thing = "world"
template: Template = t"hello {thing}"

print(repr(template))
# t"hello {'world'}"

assert template.strings[0] == "hello "
assert template.interpolations[0].value == "world"

$ python -m example
t"hello {'world'}"

Showing compiled source

future-tstrings also includes a cli to show transformed source.

$ future-tstrings example.py

Integrating with template processing tools

Libraries that consume template strings (html parsers, etc) do not need to do anything extra to support future-tstrings, except:

They should NOT disable this behavior on python<3.14. To implicitly support future-tstrings without listing it as a dependency, use the following:

try:
    from string.templatelib import Template
except ImportError:
    class Template:
        pass

How does this work?

future-tstrings has two parts:

1. An importer which transpiles t-strings and f-strings to code understood by older versions of python

2. A .pth file which registers the importer on interpreter startup.

Alternative python environments

In environments (such as aws lambda) where packages are not installed via pip, the .pth magic will not work, so you'll need to manually initialize future-tstrings in a wrapper python module. For instance:

from future_tstrings import install

install()

from actual_main import main

if __name__ == '__main__':
    main()

Additionally, for zipped or frozen packages, the importer will not work. In such environments, you will need to use the future-tstrings command-line compiler before the code is zipped, frozen, etc.