Inform — Print & Logging Utilities

Author:	Ken Kundert
Version:	1.31
Released:	2024-08-05

A package that provides specialized print functions that are used when communicating with the user. It allows you to easily print attractive, informative, and consistent error messages. For example:

>> from inform import display, warn, error
>> display(
..     'Display is like print'
..     'except that it supports logging and can be disabled.'
..     sep=', ')
Display is like print, except that it supports logging and can be disabled.

>> warn('warnings get a header that is printed in yellow.')
warning: warnings get a header that is printed in yellow.

>> error('errors get a header that is printed in red.')
error: errors get a header that is printed in red.

Inform also provides logging and output control.

In addition, Inform provides a powerful generic exception that can be used directly as a general purpose exception, or can be subclassed to produce powerful specialized exceptions. Inform exceptions are unique in that they keep all of the named and unnamed arguments so they can be used when reporting errors.

You can find the documentation on ReadTheDocs. You can download and install the latest stable version of the code from PyPI using:

pip3 install inform

You can find the latest development version of the source code on Github.

Introduction

This package defines a collection of print functions that have different roles. These functions are referred to as informants and are described below in the Informants section. They include include log, comment, codicil, narrate, display, output, notify, debug, warn, error, fatal and panic.

With the simplest use of the program, you simply import the informants you need and call them (they take the same arguments as Python's built-in print function):

>>> from inform import display
>>> display('ice', 9)
ice 9

For more control of the informants, you can import and instantiate the Inform class yourself along with the desired informants. This gives you the ability to specify options:

>>> from inform import Inform, display, error
>>> Inform(logfile=False, prog_name=False)
<...>
>>> display('hello')
hello
>>> error('file not found.', culprit='data.in')
error: data.in: file not found.

An object of the Inform class is referred to as an informer (not to be confused with the print functions, which are referred to as informants). Once instantiated, you can use the informer to change various settings, terminate the program, or return a count of the number of errors that have occurred.

>>> from inform import Inform, error
>>> informer = Inform(prog_name="prog")
>>> error('file not found.', culprit='data.in')
prog error: data.in: file not found.
>>> informer.errors_accrued()
1

You can create your own informants:

>>> from inform import Inform, InformantFactory

>>> verbose1 = InformantFactory(output=lambda m: m.verbosity >= 1)
>>> verbose2 = InformantFactory(output=lambda m: m.verbosity >= 2)
>>> with Inform(verbosity=0):
...     verbose1('First level of verbosity.')
...     verbose2('Second level of verbosity.')

>>> with Inform(verbosity=1):
...     verbose1('First level of verbosity.')
...     verbose2('Second level of verbosity.')
First level of verbosity.

>>> with Inform(verbosity=2):
...     verbose1('First level of verbosity.')
...     verbose2('Second level of verbosity.')
First level of verbosity.
Second level of verbosity.

The argument verbosity is not an explicitly supported argument to Inform. In this case Inform simply saves the value and makes it available as an attribute, and it is this attribute that is queried by the lambda function passed to the InformantFactory when creating the informants.

Exception

An exception, Error, is provided that takes the same arguments as an informant. This allows you to catch the exception and handle it if you like. The exception provides the report and terminate methods that processes the exception as an error or fatal error if you find that you can do nothing else with the exception:

>>> from inform import Inform, Error

>>> Inform(prog_name='myprog')
<...>
>>> try:
...     raise Error('must not be zero.', culprit='naught')
... except Error as e:
...     e.report()
myprog error: naught: must not be zero.

Error also provides get_message() and get_culprit() methods, which return the message and the culprit. You can also cast the exception to a string to get a string that contains both the message and the culprit formatted so that it can be shown to the user.

Any keyword arguments provided will be available in e.kwargs, but certain keyword arguments are reserved by inform (see above).

One common approach to using Error is to pass all the arguments that make up the error message as unnamed arguments and then assemble them into the message by providing a template. In that way the arguments are directly available to the handler if needed. For example:

>>> from inform import Error, did_you_mean

>>> known_names = 'alpha beta gamma delta epsilon'.split()
>>> name = 'alfa'

>>> try:
...     if name not in known_names:
...         raise Error(name, template="name '{}' is not defined.")
... except Error as e:
...     candidates = did_you_mean(e.args[0], known_names)
...     e.report(codicil = f"Did you mean {candidates}?")
myprog error: name 'alfa' is not defined.
    Did you mean alpha?

Utilities

Several utility functions and classes are provided for your convenience. They are often helpful when creating messages.

dedent:

Dedents a block of text.

indent:

Indents a block of text.

conjoin:

Like ''.join(), but allows you to specify a conjunction that is placed between the last two elements, ex:

>>> from inform import conjoin
>>> conjoin(['a', 'b', 'c'])
'a, b and c'

>>> conjoin(['a', 'b', 'c'], conj=' or ')
'a, b or c'

did_you_mean:

Given a word and list of candidates, returns the candidate that is most similar to the word.

cull:

Strips items from a collection that have a particular value.

join:

Combines the arguments in a manner very similar to an informant and returns the result as a string.

fmt:

Similar to ''.format(), but it can pull arguments from the local scope.

render:

Recursively convert an object to a string with reasonable formatting. Has built in support for the base Python types (None, bool, int, float, str, set, tuple, list, and dict). If you confine yourself to these types, the output of render() can be read by the Python interpreter. Other types are converted to string with repr().

plural:

Produces either the singular or plural form of a word based on a count.

truth:

Like plural, but for Booleans.

full_stop:

Adds a period to the end of the string if needed (if the last character is not a period, question mark or exclamation mark).

title_case:

Converts the initial letters in the words of a string to upper case while maintaining any letters that are already upper case, such as acronyms.

format_range, parse_range:

Converts a set of numbers to and from a succinct, readable string that summarizes the set. For example:

>>> from inform import format_range, parse_range

>>> format_range({1, 2, 3, 5})
'1-3,5'

>>> parse_range('1-3,5')
{1, 2, 3, 5}

columns:

Distribute array over enough columns to fill the screen.

os_error:

Generates clean messages for operating system errors.

is_str:

Returns True if its argument is a string-like object.

is_iterable:

Returns True if its argument is iterable.

is_collection:

Returns True if its argument is iterable but is not a string.

is_mapping:

Returns True if its argument is a mapping (are dictionary like).

Color:

A class is used to add color to text.

Info:

A utility class that automatically converts all keyword arguments into attributes.

ProgessBar:

A class that produces an interruptable progress bar.

render_bar:

Converts generates a text bar whose width is controlled by a normalized value.