flynt

1.0.6 verified Fri May 01 auth: no python

A CLI tool to automatically convert a Python project's %-formatted strings (like '%s' % var) and .format() calls to f-strings. Current version 1.0.6, stable, low release cadence. Requires Python >=3.9.

pip install flynt

Common errors

error flynt: error: unrecognized arguments: --line-length 80 ↓

cause The --line-length option was removed in a previous version.

fix

Remove --line-length from your command; flynt no longer supports line length control.

error TypeError: fstringify() got an unexpected keyword argument 'transform_multiline_fstrings' ↓

cause The argument was renamed or removed in a newer version of flynt.

fix

Check the API docs; use the correct argument name, e.g., 'multiline' instead.

Warnings

gotcha flynt only works on literal string expressions, not on strings stored in variables or computed at runtime. It cannot convert %-formatting inside non-literal strings. ↓

fix Ensure the strings you want to convert are explicit string literals in the source code.

gotcha flynt will modify files in-place by default. Without --dry-run, it overwrites source files, which can lead to loss of original formatting. ↓

fix Always run with --dry-run first to preview changes: flynt --dry-run <file_or_dir>

breaking flynt 1.0.6 drops Python 3.8 support; requires Python >=3.9. ↓

fix Upgrade Python to 3.9+ or pin flynt to <1.0.6 if Python 3.8 is required.

gotcha flynt may introduce syntax errors if the original string contains complex nested expressions or escaped quotes. Always verify the output. ↓

fix Run tests after conversion. Use --verbose to inspect changed files.

deprecated The --line-length option was removed in an earlier version; there is no replacement. ↓

fix Remove --line-length from command line if used.

Imports

flynt
wrong
```
from flynt import flynt
```
correct
```
import flynt
```
flynt is a module, not a function. Use as a CLI tool.

Quickstart

Basic usage: convert a single string literal to f-string.

import flynt
# flynt is a CLI tool; to run programmatically:
from flynt import fstringify
fstringify('"%s" % "hello"')