Installation and Usage¶
Installation¶
Black can be installed by running pip install black
. It requires
Python 3.6.0+ to run but you can reformat Python 2 code with it, too.
Command line options¶
Black doesn’t provide many options. You can list them by running
black --help
:
black [OPTIONS] [SRC]...
Options:
-l, --line-length INTEGER Where to wrap around. [default: 88]
--check Don't write back the files, just return the
status. Return code 0 means nothing would
change. Return code 1 means some files would be
reformatted. Return code 123 means there was an
internal error.
--fast / --safe If --fast given, skip temporary sanity checks.
[default: --safe]
--version Show the version and exit.
--help Show this message and exit.
Black is a well-behaved Unix-style command-line tool:
- it does nothing if no sources are passed to it;
- it will read from standard input and write to standard output if
-
is used as the filename; - it only outputs messages to users on standard error;
- exits with code 0 unless an internal error occured (or
--check
was used).
NOTE: This is an early pre-release¶
Black can already successfully format itself and the standard library. It also sports a decent test suite. However, it is still very new. Things will probably be wonky for a while. This is made explicit by the “Alpha” trove classifier, as well as by the “a” in the version number. What this means for you is that until the formatter becomes stable, you should expect some formatting to change in the future.
Also, as a temporary safety measure, Black will check that the
reformatted code still produces a valid AST that is equivalent to the
original. This slows it down. If you’re feeling confident, use
--fast
.