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ConfigArgParse
--------------
Overview
~~~~~~~~
Applications with more than a handful of user-settable options are best
configured through a combination of command line args, config files,
hard-coded defaults, and in some cases, environment variables.
Python's command line parsing modules such as argparse have very limited
support for config files and environment variables, so this module
extends argparse to add these features.
Available on PyPI: http://pypi.python.org/pypi/ConfigArgParse
Features
~~~~~~~~
- command-line, config file, env var, and default settings can now be
defined, documented, and parsed in one go using a single API (if a
value is specified in more than one way then: command line >
environment variables > config file values > defaults)
- config files can have .ini or .yaml style syntax (eg. key=value or
key: value)
- user can provide a config file via a normal-looking command line arg
(eg. -c path/to/config.txt) rather than the argparse-style @config.txt
- one or more default config file paths can be specified
(eg. ['/etc/bla.conf', '~/.my_config'] )
- all argparse functionality is fully supported, so this module can
serve as a drop-in replacement (verified by argparse unittests).
- env vars and config file keys & syntax are automatically documented
in the -h help message
- new method :code:`print_values()` can report keys & values and where
they were set (eg. command line, env var, config file, or default).
- lite-weight (no 3rd-party library dependencies except (optionally)
PyYAML)
- extensible (:code:`ConfigFileParser` can be subclassed to define a new
config file format)
- unittested by running the unittests that came with argparse but on
configargparse, and using tox to test with Python 3.5+
Example
~~~~~~~
*config_test.py*:
Script that defines 4 options and a positional arg and then parses and
prints the values. Also,
it prints out the help message as well as the string produced by
:code:`format_values()` to show
what they look like.
.. code:: py
import configargparse
p =
configargparse.ArgParser(default_config_files=['/etc/app/conf.d/*.conf',
'~/.my_settings'])
p.add('-c', '--my-config', required=True, is_config_file=True,
help='config file path')
p.add('--genome', required=True, help='path to genome file') # this
option can be set in a config file because it starts with '--'
p.add('-v', help='verbose', action='store_true')
p.add('-d', '--dbsnp', help='known variants .vcf', env_var='DBSNP_PATH')
# this option can be set in a config file because it starts with '--'
p.add('vcf', nargs='+', help='variant file(s)')
options = p.parse_args()
print(options)
print("----------")
print(p.format_help())
print("----------")
print(p.format_values()) # useful for logging where different
settings came from
*config.txt:*
Since the script above set the config file as required=True, lets create a
config file to give it:
.. code:: py
# settings for config_test.py
genome = HCMV # cytomegalovirus genome
dbsnp = /data/dbsnp/variants.vcf
*command line:*
Now run the script and pass it the config file:
.. code:: bash
DBSNP_PATH=/data/dbsnp/variants_v2.vcf python config_test.py
--my-config config.txt f1.vcf f2.vcf
*output:*
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