tstrings: PEP 750-style Template Strings for Python < 3.14

This package provides a backport of the new PEP 750 "t-string" template string syntax, for use with Python versions before 3.14.

Usage

Install from PyPI with uv add tstrings-backport or python -m pip install tstrings-backport.

Instead of the new syntax t"..." (which is only available in Python 3.14+), use the function call form:

from tstrings import t

name = "World"
tpl = t("Hello, {name}!")
print(tpl.strings)         # ("Hello, ", "!")
print(tpl.interpolations)  # (Interpolation(value="World", expression="name", ...),)

The returned object is a Template with .strings and .interpolations attributes, which should be a drop-in replacement for the built-in t-strings.

Features

• String interpolation: Supports {expr} expressions, including complex expressions.
• Debug specifier: {var=} and {var=:.2f} forms, as in f-strings.
• Conversion specifiers: {val!r}, {val!s}, {val!a}.
• Format specifiers: {num:.2f}.
• Multiline expressions: Supported.
• Error handling: Raises NameError or SyntaxError for invalid expressions, as in f-strings (but at runtime, not at compile time).
• PEP 750 API: Returns Template and Interpolation dataclasses matching the PEP.

Limitations

• No t-string literal syntax: You must use t("..."), not t"...".
• No support for all edge cases: Some advanced t-string edge cases may not be fully supported.

Examples

from tstrings import t

name = ""
value = 1
num = 3.1415
obj = {}
data = [1, 2, 3]

# Simple
tpl = t("Hello, {name}!")
# Debug
tpl = t("{value=}")
# Format
tpl = t("{num:.2f}")
# Conversion
tpl = t("{obj!r}")
# Multiline
tpl = t("""
    {sum(data)}
""")

Development & Testing

Install with uv sync and activate the virtualenv (. .venv/bin/activate or similar).

Run the test suite with:

make test

or just:

uv run --python 3.13 pytest

See tests/test_all.py for coverage of all supported features.

Tests also include the tdom source code (modified for pre-3.14 syntax) and test suite.

How to help

This was (initially) hacked together in less than 2 hours. If you find it useful, please consider contributing fixes, improvements, or documentation!

Pull requests and issues are welcome.