Commandlines Library Documentation

commandlines

Source Repository: chrissimpkins/commandlines

Documentation: commandlines.github.io

What is Commandlines?

Commandlines is a Python library for command line application development that supports command line argument parsing, command string validation testing, & application logic. It has no external dependencies and provides broad Python interpreter support for Python 2.6+, Python 3.3+, pypy, and pypy3 across OS X, Linux, and Windows platforms.

The library supports application development with POSIX guideline compliant[1] command argument styles, the GNU argument style extensions to the POSIX guidelines (including long option syntax and variable position of options among arguments), and command suite style application arguments that include one or more sub-commands to the executable.

How Do I Use It?

The command line string to your executable script is parsed to multiple objects that are derived from builtin Python types.

The Command Object

Instantiate a commandlines Command object:

from commandlines import Command

c = Command()

and use the following instance attributes and methods to develop your application:

Arguments

Positional Arguments

Positional arguments use a 0 based index starting at the first argument to the executable (i.e. sys.argv[1:]) and are maintained as attributes in the Command object. Individual attribute support is provided for the first five positional arguments and the last positional argument. An ordered list of all positional arguments is available in the arguments attribute.

Default Option-Argument Definitions

Define option-argument defaults in a defaults Command instance attribute. This attribute is defined as an empty Python dictionary upon instantiation of the Command object. Use standard key index-based Python dictionary assignments or the set_defaults assignment method in the Command class to define default values. Default values can take any type that is permissible as a Python dictionary value.

Here are examples of each approach that define defaults for output and level options:

Key Index-Based Default Assignments

from commandlines import Command

c = Command()

c.defaults['output'] = "test.txt"
c.defaults['level'] = 10

Method-Based Default Assignments

from commandlines import Command

c = Command()

default_options = {
    'output' : 'test.txt',
    'level'  : 10
}
c.set_defaults(default_options)

To test for the presence of a default option definition and obtain its value, use the contains_defaults and get_default methods, respectively:

# continued from code examples above

if c.contains_definitions('output'):
    dosomething(c.get_definition('output'))
elif c.contains_defaults('output'):
    dosomething(c.get_default('output'))
else:
    dosomethingelse()

Help, Usage, and Version Request Testing Methods

Help, usage, and version command line requests are tested with methods:

Testing Methods for Other Commonly Used Switches

Special Command Line Idioms

The double dash idiom escapes all subsequent tokens from option/argument parsing. Methods are available to determine whether a double dash token is present in a command and obtain an ordered list of all command line arguments that follow this idiom:

Application Logic Testing Methods

Command String Validation Methods

Development with Commandlines

To facilitate development with Commandlines, you can print the string returned by the Command obj_string() method to view a list of the parsed arguments from example commands:

from commandlines import Command

c = Command()

print(c.obj_string())
sys.exit(0)

For example, if you execute your script with the command spam eggs --toast -b --drink=milk filepath and include the above print statement in your source, you will see the following in your terminal emulator:

$ spam eggs --toast -b --drink=milk filepath
obj.argc = 5
obj.arguments = ['eggs', '--toast', '-b', '--drink=milk', 'filepath']
obj.defaults = {}
obj.switches = {'toast', 'b'}
obj.defs = {'drink': 'milk'}
obj.mdefs = {}
obj.mops = {}
obj.arg0 = 'eggs'
obj.arg1 = '--toast'
obj.arg2 = '-b'
obj.arg3 = '--drink=milk'
obj.arg4 = 'filepath'
obj.arglp = 'filepath'
obj.subcmd = 'eggs'
obj.subsubcmd = '--toast'

API Documentation

You can view full documentation of the Command class here.

If you would like to dig into lower level objects in the commandlines package, you can view the library API documentation.

Exceptions that are used in the commandlines package are documented here.

How to Include Commandlines in Your Project

For Projects That Will Be Distributed to Others

Add the commandlines package dependency to your project setup.py file in the install_requires field like so:

setup(
    ...
    install_requires=["commandlines"],
    ...
)

Then, enter the following command to test your project locally:

$ python setup.py develop

Import the commandlines package in your project and instantiate a Command object by adding the following lines to your Python script:

from commandlines import Command

c = Command()

And away you go...

The Commandlines package will be installed automatically for users who install your releases via pip or your project setup.py file (i.e. with the command $ python setup.py install).

For Local Projects That Are Not Intended for Redistribution

Install the Commandlines package with the command:

$ pip install commandlines

Import the commandlines package in your project and instantiate a Command object by adding the following lines to your Python script:

from commandlines import Command

c = Command()

License

Commandlines is licensed under the MIT license.

[1] with the exception of the short single option-argument definition syntax that does not include an intervening space character (e.g. -ofile)