In most cases, there is very little to configure when creating a new Prompt instance. The defaults will use standard input and output and will not record any tag information passed into write calls. Simply instantiate and use:

p = Prompt()
p.write('Goodbye World')
name ='What is your name?')

Text Modifiers

A few methods are used to modify text but not actually write it. The intention here is to chain them together to pre-format the text. For example:

p.write('Important', COLOR_RED)))

In some cases, shortcuts are provided in the write methods themselves:

p.write('Important', color=COLOR_RED)

Keyboard Interrupts

By default, Okaara will intercept KeyboardInterrupt exceptions (i.e. if the user presses ctrl+C) and return to the caller a reference to the ABORT object in the prompt module. This lets the caller easily distinguish between an empty input from the user (will be an empty string) versus the user cancelling during the read. This behavior can be overridden to allow KeyboardInterrupt exceptions to be raised using the interruptable flag on the read method.

For a quick example:

from okaara.prompt import Prompt, ABORT
p = Prompt()

age ='How old are you?')
if age is ABORT:
  p.write('Fine, be like that.')


The prompt module defines a number of constants used for coloring text. The COLOR_* variables should be the only values passed to either the color method or the color attribute on the write method.

If the prompt is configured to not display colors (enable_color in the constructor), all calls to the color method will not apply the color formatting. There is no need to manually decide whether or not to make the color call, the prompt instance will take care of enabling/disabling them for you.


I’m a compulsive unit tester, so I wanted to provide an answer for some of the difficulties in unit testing a user interface.

Testing Output

One option to assert the output displayed to a user is to capture it and compare it against expected results. This can get wonky as the UI evolves and phrasing changes.

Okaara addresses by allowing a tag to be specified to each write call. The tag should be something simple to identify what is being displayed in the call. During unit testing, the prompt can be configured to capture these tags and make them available in the test verification step.

For example, given the following UI:

def validate(value):
  if value > 0:
    p.write('Entered value was acceptable', tag='success')
    p.write('Invalid value, exiting', tag='error')

In the test case for this UI, recording of tags would be enabled and the test would verify the correct output was displayed by checking the tags:

p = Prompt(record_tags=True)
client = MyClient(p)

self.assertEqual('success', p.get_read_tags()[0])

Testing Input

The same tagging concept for writing is available to reading user input as well. There is a corresponding get_write_tags method for retrieving these tags.

The prompt module also provides the Script class to aid in testing. An instance of this class is pre-populated with the lines a simulated user would input. The instance is passed as the input parameter to the Prompt class. Each time the prompt attempts to read a value the script will pop the next string off the list of lines provided.

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