This is an alpha release. Do NOT use on uncommitted code!

fstringify is a command line tool to automatically convert a project's Python code from old "%-formatted" strings into Python 3.6+'s "f-strings".

Here's a complete diff running it against flask.

I mainly wanted an excuse to play with the built-in AST and tokenze modules. That said, f-strings are really cool. To quote Joanna Jablonski's great f-string guide:

Not only are they more readable, more concise, and less prone to error than other ways of formatting, but they are also faster!

fstringify can be installed by running pip install fstringify. It requires Python 3.6.0+ to run and effectively turns the code it runs on into Python 3.6+, since 3.6 is when "f-strings" were introduced.

To run: fstringify {source_file_or_directory}

usage: fstringify [-h] [--verbose | --quiet] [--version] src

fstringify 0.x.x

positional arguments:
  src         source file or directory

optional arguments:
  -h, --help  show this help message and exit
  --verbose   run with verbose output
  --quiet     run without output
  --version   show version and exit

• astor is used to turn the transformed AST back into code.
• black was a big inspiration, but is only used as a dependency for forcing double quotes when they are used as the input code.