Py-qanda

Simple commandline questions

Attention

This article has been imported from a different format on a previous website and has not yet been checked. It may be malformed or incomplete.

Having grown tired on writing (and rewriting) functions to ask users for a file name, menu choice etc., I''ve broken out the functionality into a single reusable package. Here 'tis.

Background

Interactive command-line programs need to query users for information, be it text, choices from a list, or simple yes-or-no answers. qanda [qanda-home, qanda-pypi] module of simple functions to prompt users for such information, allowing validation and cleanup of answers, default responses, consistent formatting and presentation of help text, hints and choices. It is not a replacement for textual interfaces like curses and urwid, but intended solely for simple console scripts with user input is required.

Status: qanda is in use by one other non-trivial library, and so is functional. However this is still an early release and the API may change. Comment is invited.

Installation

The simplest way to install qanda is via easy_install or an equivalent program:

% easy_install qanda

Alternatively the tarball can be downloaded, unpacked and setup.py run:

% tar zxvf qanda.tgz
% cd qanda
% python set.py install

qanda has no prerequisites and should work with just about any version of Python.

Using qanda

A full API is included in the source distribution.

An example

>>> from qanda import prompt
>>> prompt.string ("What is your name")
What is your name: Foo
>>> fname = prompt.string ("Your friends name is",
    help="I need to know your friends name as well before I talk to you.",
    hints="first name",
    default='Bar',
)
I need to know your friends name as well before I talk to you.
Your friends name is (first name) [Bar]:
>>> print fname
Bar
>>> years = prompt.integer ("And what is your age", min=1, max=100)
And what is your age: 101
A problem: 101 is higher than 100. Try again ...
And what is your age: 28

Central concepts

qanda packages all question-asking methods in a Session class. This allows the appearance and functioning of all these methods to be handled consistently and modified centrally. However, you don't necessarily have to create a Session to use it - there's pre-existing Session in the variable called prompt:

>>> from qanda import Session
>>> s = Session()
>>> from qanda import prompt
>>> type (prompt) <class 'qanda.session.Session'>

The question methods are named after the type of data they elicit:

>>> print type(prompt.integer ("Pick a number"))
Pick a number: 2
<type 'int'>
>>> print type (prompt.string ("Pick a name"))
Pick a name: Bob
<type 'string'>

Many of the question methods with accept a list of "converters", each of which is used to successively transform or validate user input. This follows the idiom of Ian Bicking's FormEncode: raw values are passed into  a converter and the results are passed into the next. If input fails validation, the question is posed again. qanda supplies a number of basic validators:

ToInt, ToFloat
Convert inputs to other types
Regex
Only allow values that match a certain pattern
Range
Check that input falls within given bounds
Length
Check that input length falls within given bounds
Synonyms
Map values to other values
Vocab
Ensure values fall within a fixed set