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oitnb works around some of black's issues

Project description

The uncompromising code formatter Black has very many good points, but by design it is not very flexible. If you cannot accept it as is, oitnb might be an alternative for you.

In short, on top of Black’s features, oitnb:

  • defaults to single-quotes, but allows you to select double-quotes for strings (triple quotes and an empty string use double-quotes). Option --double.

  • allows you to run meld for visual comparison of reformatted code, so you can easily insert some # fmt: off at appropriate places. Option --meld.

  • reads your configuration in a format that you already know (Python) from a file that you most likely already have in your project anyway (

  • have project spanning base defaults in your configuration directory (XDG). That is e.g. where your line-length goes, that is carefully brought in sync with your editor width, the width of the three terminals fitting on your screen or your multi-file diff utility.

  • makes displaying icons optional. They might not display in your terminal in the first place, or not fit your professional environment.

  • has support for diffing against version committed to the project before starting to use oitnb

Work-in-progress/things planned:

  • triple quotes multi-line strings that start after the left parenthesis of a function. Option --multi-line-unwrap. (A must if you write a lot of in-file , dedented, strings with YAML, as e.g. YAML library developer would.)

  • control spreading of multi-element list to one per line

  • your wish here (we can always make it a configuration option, command-line option)

  • keep alignment of EOL comments


Code base

oitnb code is directly derived from Black’s and uses many files as-is.

It can run most of Black’s tests without problems but there is a handful of errors, which should all have to do with hard-coded references to Black in both file content and file naming.

Extra options, defaults and configuration

extra options: --double, --meld, --multi-line-unwrap

oitnb defaults to single-quotes around strings, if you want to use the quoting like Black has use the option --double option.

--meld which works like --diff, but for the invocation of meld on the original file and the reformatted version. meld allows you to directly edit the left hand side (original) so you can at that point decide to insert some # fmt: off / # fmt: on comments around lines, or to abandon the use of a formatter altogether.

Specifying --multi-line-unwrap runs an ugly post-processor on the reformatted lines undoing the rewrite of:

x = yaml.load("""
a: 1
b: 2


x = yaml.load(
a: 1
b: 2

The program starts with an empty config dict and tries to read the basic configuration from oitnb.pon in the user config dir using appdirs.user_config_dir. This adheres to the XDG standard on Linux (i.e. ~/.config/oitnb) if no environment variables are set to change the defaults. That file should contain a valid Python dict definition ( with {} or dict(), and from this dict the value for default is taken (using safe evaluation) to update the config dict:

   default=dict(line_length=666, double=True),

After that the directory hierarchy up-the-tree is searched until .git is found, or .hg or an file with a module level definition of _package_data. That should be a dict and from there the value for the key oitnb is taken to update the config:

_package_data = dict(

oitnb’s has more information there used (without import-ing!), and programmatically updated, by other tools:

_package_data = dict(
    version_info=(0, 1, 1),
    author='Anthon van der Neut',
    description="oitnb works around some of black's issues",
    package_data={"_oitnb_lib2to3": ["*.txt"]},
    install_requires=['click>=6.5', 'attrs>=17.4.0', 'appdirs', 'toml>=0.9.4'],

version_info = _package_data['version_info']
__version__ = _package_data['__version__']

On top of this, any command-line options are used to overrule the config, and then the program is initialised.

Dashes (-) in options are internally replaced by underscore (_), you can use that form as key in dict(op_tion=True). With dashes you would need to use {“op-tion”: True}

There is currently no computer wide, setting for defaults, such as /etc/xdg/oitnb (is anyone sharing their development machines these days?).

Finding changes against pre-oitnb revisions

If you have an existing project with revision history, and apply oitnb to your sources, then diffing between pre- and post-oitnb versions is going to be cluttered.

If your application of oitnb was applied without Internal errors, and if you did not have to apply # fmt: no to often, then you can use the following to get more useful visual diffs using meld.

The installation of oitnb includes a minimal utility omeld, add this as an external diff tool to your mercurials .hgrc file:

hgext.extdiff =

cmd.omeld =

Now you can execute hg omeld -r-4 -r-1 or hg omeld -r-4 (assuming revision -4 was from before applying oitnb) and omeld will run oitnbt on both temporarily created source trees, before handing those trees over to meld. That means e.g. that any source changes regarding quotes or removal of superfluous u’s from u’’ strings, rewrapping, etc. are going to be the same for both sides of the revisions. Thereby leaving the real code changes in the diff that meld presents.

If the omeld tools gets a file or directory as argument that is not under /tmp or /var/tmp, it will not run oitnb on that file/directory. If you keep your source tree under /var/tmp, you are out of luck: your python will be formatted.

The above approach: check out both (old) revisions trees, code format them with ``oitnb`` and run a diff, is generic. meld and mercurial are just the tools I use and can easily provide a working setup for.

For git, which in my experience is a bit more difficult to get to understand multiple external difftools, you can do:

alias gomeld='git difftool --extcmd=omeld -y'

and use that alias.

git seems somewhat more optimised than hg in that if the current checked out version of a file is the same as one of the reversions asked, that it will not make a temporary version (not even if you have to compare multiple files). Versions before 0.1.4 should therefore not be used with the above alias, as those may result updated files in your source tree (which should not break anything, but not be what you expected).

Problems you might encounter with Black

Double-quotes everywhere

If you use single-quotes for your strings you are in good company: “People use to really love double quotes. I don’t know why.. And as PEP8 has the following to say about quotes around strings:

In Python, single-quoted strings and double-quoted strings are the same. This PEP
does not make a recommendation for this. Pick a rule and stick to it.

Googling for Stick to it: continue or confine oneself to doing or using a particular thing.

It is not just the consistency of confining yourself, it is also the long term continuation.

Unwrapping where a second line might do

If you have a list of short strings that fit on a line and add one so that it doesn’t fit anymore,














on a new line. Just putting the added overflow on a new line is good enough in those cases.

Funny characters

The Unicode in the messages might not display in the font you’re using (they did not for me with Inconsolata in my Gnome Terminal). Do you know what those code-points should show? If not, are you sure that when using Black on a different computer, while the person who pays you for your work looks over your shoulder, that you’ll not be embarrassed (or get into trouble if e.g. they were code-points U+5350 or U+0FD5)?

You might find seeing the SLEEPING FACE (U+1F634), SHORTCAKE (U+1F370), COLLISION SYMBOL (U+1F4A5), BROKEN HEART (U+1F494), SPARKLES (U+2728) interesting for a while. But especially when using a small font in order not to scroll too much the details become blurry and no-fun.

Little configurability

The configurability of Black consists inserting lines in Yet Another Markup Format that adds nothing to the existing spectrum in Yet Another Config File cluttering your project directory.

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