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.

This api may be unstable until the release of python 3.14 to ensure it is fully compatible.

Installation

pip install future-tstrings

Usage

Include the following encoding cookie at the top of your file (this replaces the utf-8 cookie if you already have it):

# -*- coding: future-tstrings -*-

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

- example.py

# -*- coding: future-tstrings -*-
thing = 'world'
template = t'hello {thing}'
print(template)

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

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

Showing transformed source

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

$ future-tstrings example.py
thing = 'world'
print('hello {}'.format((thing)))

How does this work?

future-tstrings has two parts:

1. A utf-8 compatible codec which performs source manipulation
   • The codec first decodes the source bytes using the UTF-8 codec
   • The codec then leverages the parso library to recompile the t-strings and f-strings.
2. A .pth file which registers a codec on interpreter startup.

when you aren't using normal site registration

in setups (such as aws lambda) where you utilize PYTHONPATH or sys.path instead of truly installed packages, the .pth magic above will not take.

for those circumstances, you'll need to manually initialize future-tstrings in a python file that does not use them. For instance:

from future_tstrings.installer import install

install()

from actual_main import main

if __name__ == '__main__':
    main()