A tool that applies the Black python source code formatter to a single piece of python source code instead of a whole file or project.

Usage

$ pip install blacken-selection
$ blacken-selection -h
usage: Apply the black code formatter for a piece of python source code

positional arguments:
  SOURCE                The python source code to be formatted. If not
                        provided then source is read from stdin.

optional arguments:
  -h, --help            show this help message and exit
  -l LINE_LENGTH, --line-length LINE_LENGTH
                        How many characters per line to allow. [default: 88]
$ blacken-selection "def main(): pass"
def main():
    pass

Usage from PyCharm on linux

Unfortunately PyCharm External Tools cannot be used directly. The $SelectedText$ macro passes the selection as a command line argument to the tool but there is no way to properly quote a python string using double quotes.

But there is a solution:

• Install the xclip command line tool, we will use it to grab the code selection in PyCharm via the clipboard
• Install blacken_selection as described above
• Grab the simple shell script blacken-selection-xclip.sh

Setup blacken-selection-xclip.sh as an external tool in PyCharm:

File -> Settings -> Tools -> External Tools

Click the + icon to add a new external tool with the following values:

    Name: blacken
    Description: Blacken a piece of python code
    Program: <absolute path for your blacken-selection-xclip.sh>
    Arguments:

Select a piece of python source code in your editor and from the right click context menu select:

External Tools -> blacken

Or you can confiugre a shortcut (e.g. Shift+Alt+B) to trigger the tool in:

Settings -> Keymap-> External Tools -> blacken

The tool will grab the selected text form the clipboard, format it with black, and the copy the formatted code back to the clipboard. So you can basically do the select, shift+alt+B, insert in PyCharm to format a piece of python code with black.