Flags

Flag is a boolean parameter which is toggled by single keyword. There are supported both short (-f) and long (--force) formats.

In order to create flag rule specification, use:

from nuclear import flag

flag(
        *keywords: str,
        help: str = None,
        multiple: bool = False,
)

keywords are arguments (one or many) which any of them enables flag when it occurs. Flag value is False by default. Flag keywords may be passed using direct format: -f or --flag, as well as by name: f or flag, which will be also evaluated to -f or --flag. Single character flags will get single hyphen prefix (-f), longer flag names will get double hyphen prefix (--flag).

help is description of the flag displayed in help output

multiple - whether flag is allowed to occur many times. Then flag has int type and stores number of its occurrences

Example:

from nuclear import CliBuilder, flag

CliBuilder(run=lambda force: print(force)).has(
    flag('--force', '-f'),
).run()

Usage:

foo@bar:~$ ./example.py --force
True
foo@bar:~$ ./example.py
False

Combining short flags

Many short flags may be combined in one argument. Instead of -t -u -l -p -n you can just type -tulpn.

Multiple flag occurrences

Multiple occurences are also supported for flags. When multiple is set to True, then the flag value represents how many times it was set. The value type is then int, not bool.

CliBuilder(run=lambda verbose: print(f'verbosity level: {verbose}')).has(
    flag('verbose', 'v', multiple=True),
).run()

Then -vvv should return 3.

See flag tests for more detailed use cases.