Improving function as a keyword

Summary

This builds upon our previous example of allowing function to being equivalent to lambda.

This example demonstrates the use of passing back parameters to an import hook and some possible usage.

Source code

Basic usage:

from ideas.examples import function_keyword
function_keyword.add_hook()

import my_program

Building a complete example

In addition to making it easy to create import hooks, ideas also attempts to make it easy to include diagnostic “tools”. The function_keyword example, whose API listed below includes links to the actual source, includes such “tools”. While they can help during development, they do admitedly make the code more complicated. If you want to create your own hook, you do not have to include all possible features.

For example, here is a much simpler version, functionally equivalent the function_keyword example, but without some diagnostic options included:

from ideas import import_hook, token_utils

def transform_source(source, **kwargs):
    new_tokens = []
    for token in token_utils.tokenize(source):
        if token == "function":
            token.string = "lambda"
        new_tokens.append(token)
    return token_utils.untokenize(new_tokens)


def add_hook():
    return import_hook.create_hook(transform_source=transform_source)

Note the unused **kwargs in the definition of transform_source: you should ensure to add something similar when creating your own import hook even if you do not plan to make use of extra parameters.

Verbose finder

Suppose you want to see information about names and paths of files that are searched by your Finder: you can do this by adding an extra parameter to add_hook and import_hook.create_hook as follows:

def add_hook(verbose_finder=False):

    return import_hook.create_hook(
        transform_source=transform_source,
        verbose_finder=verbose_finder,
    )

Here’s a sample session from a different example, where the import hook is looking for files with a custom extension:

>>> from ideas.examples import french
>>> hook = french.add_hook(verbose_finder=True)
Looking for files with extensions:  ['.pyfr']
The following paths will not be included in the search:
   PYTHON: == c:\users\andre\appdata\local\programs\python\python37-32\lib
   IDEAS: == c:\users\andre\github\ideas\ideas
>>> import mon_programme
    Searching for TESTS:\french\mon_programme.pyfr.
->  Found:  TESTS:\french\mon_programme.pyfr

    Searching for TESTS:\french\unicodedata.pyfr.
  IdeasMetaFinder did not find unicodedata.

The last file that was needed was unicodedata.py from the Python standard library; it was found by a “normal” finder used by Python.

Comparing the original and the transformed source

pattern != actual code

The code used is slightly different than was is shown here.

It might be sometimes useful to compare the original source with the transformed one. Instead of actually adding print statements when needed, we can use some callback parameters to enable or disable such print statemeent. ideas makes it fairly easy to do this using callback parameters. Here’s the basic pattern used in almost all the examples:

def transform_source(source, callback_params=None, **kwargs):
    if callback_params is not None:
        if callback_params["show_original"]:
            print(source)

    new_source = do_transform(source)

    if callback_params is not None:
        if callback_params["show_transformed"]:
            print(new_source)
    return new_source


def add_hook(show_original=False, show_transformed=False):
    callback_params = {
        "show_original": show_original,
        "show_transformed": show_transformed,
    }
    hook = import_hook.create_hook(
        transform_source=transform_source,
        callback_params=callback_params,
    )
    return hook

Here’s an actual example using one such parameter to show the transformed source:

>>> from ideas.examples import function_keyword
>>> hook = function.add_hook(show_transformed=True)
>>> from ideas import console
>>> console.start()
Configuration values for the console:
    callback_params: {'show_original': False, 'show_transformed': True}
    transform_source from ideas.examples.function
--------------------------------------------------
Ideas Console version 0.0.4. [Python version: 3.7.3]

~>> square = function x: x**2
===========Transformed============
square = lambda x: x**2
-----------------------------
~>> square(3)
===========Transformed============
square(3)
-----------------------------
9
~>>