This is a work in progress. Use at your own risk.

ext_pylib is a group of submodules that are useful scaffolding for other larger projects. I began developing it after noticing how often I was repeating several patterns for server scripts. It works well for building server scripts.

It contains basic classes for files, directories, and domain names as well as helpful functions for prompting and displaying terminal data. It also contains some functions in the meta module for meta programming.

$ pip install ext_pylib

$ cd <ext_pylib directory>
$ py.test

The domain module consists of the class Domain(). It is used for binding an IP and a domain name in one object. It requires one paramater at initialization: the domain name as a string.

Future: There are tentative plans for including a wrapper for DNS API's such as Rackspace's API.

Also included in this module is the function get_server_ip(). This function is designed to get the public IP of the server. It works by making an http request to a url that returns only the IP address as a string. It takes one parameter: get_ip_urls a list of one or more urls to use.

A class to manage and create files. Also includes three mixin classes Parsable, Section, and Template.

The Section mixin adds methods useful for processing template section files. A section file is a template of a configuration file that only represents a particular section of that file. It begins and ends with a delineator

For example:

## START:SECTION_NAME ##
content here...
## END:SECTION_NAME ##

A use case would be how WordPress delineates a particular section of the htaccess file in its root directory with a start line and an end line. This is a section of the full htaccess file and could be managed by a Section mixin.

The Template mixin adds a method useful for processing a regular template file: apply_using(). It assumes that the file contains placeholder text to be replaced by actual data. The placeholders and actual data are passsed into the method as a dict. The resulting data is returned (presumably to be saved in another file.)

The Parsable mixin adds a method useful for parsing (presumably) configuration files. It takes a dict of attribute names and regexes to be used. When setup_parsing() is called, a dynamic property is created for getting and setting a value in self.data based on the regex.

The prompts module contains a number of helpful functions for prompting for user input.

The prompt() function prints a prompt question and expects the user to type a 'yes' or 'no' answer. It requires a string passed as the text to be displayed. The default response (just pressing enter) is 'yes' (true). This default can be changed by passing the attribute default=False. The function returns a bool cooresponding to the appropriate value.

The prompt_str() function prints a prompt and expects the user to type a string. It requires a string passed as the text to be displayed. It also takes an optional default value that can be set to a default string. If the user just presses enter the default string is used. The function returns the string that the user typed (or the default string).

The warn_prompt() function is similar to the prompt_str() function.

The meta module is useful for meta programming. This module is experimental. It has the object DynamicPropery which is a close reimplementation of Python's native property(). It allows creating a class property on the fly. It is initialized with a getter function to return the property value and a setter function can be initialized by calling create_setter() on the property itself. Note that this must be done on the class not an instance of the class.

Credit for much of this object goes to: http://eev.ee/blog/2012/05/23/python-faq-descriptors/

The best way to understand this object is to look at an example:

from ext_pylib.meta import DynamicProperty

def getter_func(self):
    return self._property

def setter_func(self, value):
    self._property = value

class Cls(object): pass
instance = Cls()
instance.__class__.new_property = DynamicProperty(getter_func)
instance.__class__.new_property = instance.__class__.new_propety.create_setter(setter_func)

instance.new_property = 'value'
print instance.new_property  # prints: 'value'

This module also has the function setdynattr() which is a convenient wrapper around the DynamicProperty class. It takes an object, an attribute (as a string), and optional getter and setter functions. If the getter and setter functions are not supplied, default getter and setter functions are used that merely get and set an attribute with the name '_' + attribute.

The password module has the function generate_pw() for generating a relatively strong pseudo-random password. This function takes two optional parameters. The length parameter determines how long the password will be. It defaults to 18 characters. The char_set is a dict of a string of characters to use as a set. These are the set (as a python string) of characters that will not appear twice in a row in the generated password. The default character set has a set of numbers, lowercase letters, uppercase letters, and special characters. This prevents having a password with two numbers in a row or two lowercase characters in a row and makes the password stronger. Leaving the char_set as default is good for most circumstances, although it may be necessary to change it for various password restrictions.

The default character set is:

DEFAULT_CHAR_SET = {
    'small': 'abcdefghijklmnopqrstuvwxyz',
    'nums': '0123456789',
    'big': 'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
    'special': '^!$%&=?{[]}+~#-_.:,;<>|'
}

The terminal module is a collection of functions that aid in modifying the terminal output and as well as adding color and text effects. It is made up of two seperate modules, the ansi module and the colors module.

Because of the interactive nature of this module, the tests must be called directly:

$ cd <ext_pylib directory>/terminal
$ python ./interactive_test.py

The ansi module contains a number of constants representing ANSI excape codes and functions for printing them to the screen. Most of the functions take an optional parameter get_string which defaults to False and indicates that the escape will be printed to the screen. When this is set to True, the function will return a string. Some of the functions, such as the cursor functions, take optional integer parameters. These functions are relatively straightforward.

• cursor_hide(get_string=False) - hides the cursor
• cursor_show(get_string=False) - shows the cursor
• cursor_up(n=1, get_string=False) - moves your cursor up 'n' cells
• cursor_down(n=1, get_string=False) - moves your cursor down 'n' cells
• cursor_right(n=1, get_string=False) - moves your cursor right (forward) 'n' cells
• cursor_left(n=1, get_string=False) - moves your cursor left (backward) 'n' cells
• cursor_next_line(n=1, get_string=False) - moves your cursor to the next 'n' lines
• cursor_previous_line(n=1, get_string=False) - moves your cursor to the previous 'n' lines
• cursor_horizontal_absolute(n=1, get_string=False) - moves your cursor to the 'n' column
• cursor_position(x=0, y=0, get_string=False) - Moves youescape = cursor to position (x, y) NOTE: This assumes starting at (0, 0) which is different than the ANSI standard; it also assumes (x, y) and not (y, x) per ANSI standard.
• cursor_save(get_string=False) - save the current cursor position
• cursor_restore(get_string=False) - restore the last saved cursor position
• attributes_save(get_string=False) - save the current cursor position and attributes
• attributes_restore(get_string=False) - restore the last saved cursor position and attributes
• get_cursor_pos() - returns a tuple of (x, y) of current cursor position NOTE: this follows conventional (x, y) order and starts with (0, 0) and not the order according to the ANSI standard.

• clear(get_string=False) - clears the entire screen
• clear_down(get_string=False) - clears the screen from the cursor down
• clear_up(get_string=False) - clears the screen from the cursor down
• clear_line(get_string=False) - clears the entire line
• clear_line_forward(get_string=False) - clears the entire line
• clear_line_back(get_string=False) - clears the entire line
• reset(get_string=False) - clears the entire screen and places cursor at top left corner

• reset_terminal(get_string=False) - resets the terminal
• enable_line_wrap(get_string=False) - enables line wrapping
• disable_line_wrap(get_string=False) - disables line wrapping
• set_scroll_all(get_string=False) - enable scrolling for the entire screen
• set_scroll(start_row, end_row, get_string=False) - enable scrolling from start_row to end_row
• scroll_up(get_string=False) - scrolls up
• scroll_down(get_string=False) - scrolls down

The colors module contains a number of functions for printing color to the screen. These functions require a string to be colored and will return a string with the appropriate color. The functions can be infinitely nested or passed as optional additional arguments from any of the other functions. Note that it is possible to mix combinations that don't make sense. A string cannot be both green and red. The last (or innermost) escape sequence is the one that will affect the display.

For example:

print green('This text will be green')

# More complicated examples:
print bold('WARN:', red) + red_on_white('This is an example warning.')
print underline(green(on_blue('This is an example of nesting color functions.')))
print blue('This is an example of passing color functions to another function.', on_black, bold)

• normal(string, *funcs, **additional)
• underline(string, *funcs, **additional)
• bold(string, *funcs, **additional)
• blink(string, *funcs, **additional)
• rblink(string, *funcs, **additional)
• reverse(string, *funcs, **additional)
• conceal(string, *funcs, **additional)

• black(string, *funcs, **additional)
• red(string, *funcs, **additional)
• green(string, *funcs, **additional)
• yellow(string, *funcs, **additional)
• blue(string, *funcs, **additional)
• magenta(string, *funcs, **additional)
• cyan(string, *funcs, **additional)
• white(string, *funcs, **additional)

• on_black(string, *funcs, **additional)
• on_red(string, *funcs, **additional)
• on_green(string, *funcs, **additional)
• on_yellow(string, *funcs, **additional)
• on_blue(string, *funcs, **additional)
• on_magenta(string, *funcs, **additional)
• on_cyan(string, *funcs, **additional)
• on_white(string, *funcs, **additional)

• red_on_black(string, *funcs, **additional)
• green_on_black(string, *funcs, **additional)
• yellow_on_black(string, *funcs, **additional)
• blue_on_black(string, *funcs, **additional)
• magenta_on_black(string, *funcs, **additional)
• cyan_on_black(string, *funcs, **additional)
• white_on_black(string, *funcs, **additional)
• black_on_red(string, *funcs, **additional)
• green_on_red(string, *funcs, **additional)
• yellow_on_red(string, *funcs, **additional)
• blue_on_red(string, *funcs, **additional)
• magenta_on_red(string, *funcs, **additional)
• cyan_on_red(string, *funcs, **additional)
• white_on_red(string, *funcs, **additional)
• black_on_green(string, *funcs, **additional)
• red_on_green(string, *funcs, **additional)
• yellow_on_green(string, *funcs, **additional)
• blue_on_green(string, *funcs, **additional)
• magenta_on_green(string, *funcs, **additional)
• cyan_on_green(string, *funcs, **additional)
• white_on_green(string, *funcs, **additional)
• black_on_yellow(string, *funcs, **additional)
• red_on_yellow(string, *funcs, **additional)
• green_on_yellow(string, *funcs, **additional)
• blue_on_yellow(string, *funcs, **additional)
• magenta_on_yellow(string, *funcs, **additional)
• cyan_on_yellow(string, *funcs, **additional)
• white_on_yellow(string, *funcs, **additional)
• black_on_blue(string, *funcs, **additional)
• red_on_blue(string, *funcs, **additional)
• green_on_blue(string, *funcs, **additional)
• yellow_on_blue(string, *funcs, **additional)
• magenta_on_blue(string, *funcs, **additional)
• cyan_on_blue(string, *funcs, **additional)
• white_on_blue(string, *funcs, **additional)
• black_on_magenta(string, *funcs, **additional)
• red_on_magenta(string, *funcs, **additional)
• green_on_magenta(string, *funcs, **additional)
• yellow_on_magenta(string, *funcs, **additional)
• blue_on_magenta(string, *funcs, **additional)
• cyan_on_magenta(string, *funcs, **additional)
• white_on_magenta(string, *funcs, **additional)
• black_on_cyan(string, *funcs, **additional)
• red_on_cyan(string, *funcs, **additional)
• green_on_cyan(string, *funcs, **additional)
• yellow_on_cyan(string, *funcs, **additional)
• blue_on_cyan(string, *funcs, **additional)
• magenta_on_cyan(string, *funcs, **additional)
• white_on_cyan(string, *funcs, **additional)
• black_on_white(string, *funcs, **additional)
• red_on_white(string, *funcs, **additional)
• green_on_white(string, *funcs, **additional)
• yellow_on_white(string, *funcs, **additional)
• blue_on_white(string, *funcs, **additional)
• magenta_on_white(string, *funcs, **additional)
• cyan_on_white(string, *funcs, **additional)

The usermodule consists of two wrapper functions. get_current_username() returns the current user as a string. get_current_groupname() likewise returns the current user's group as a string.

Soli Deo gloria.