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pydemo

Python code demonstration console for didactic purposes. Prints and executes input files in blocks.

Description

pydemo provides a command line interpreter which emulates the behavior of the interactive Python interpreter. In addition, it can read files Python files and execute them by blocks. The CLI processes all the files and splits them in code blocks. A certain number of empty lines in files (1 by default) are used to identify the boundaries between blocks, although they are also validated to verify that they are syntactically correct. In negative case, next lines are added until the accumulated block is right. Each time no text is introduced in the CLI (just pressing ENTER key) a new block is executed. It is print (with syntax highlighted if Pygments is installed) and then it is evaluated inside the CLI, so that in next command you may use objects instantiated inside the code block.

Installation

Download the code and execute python setup.py install. After installation you will have a pydemo command available.

Requirements

  • pydemo is not compatible with Python 3.X (migration pending):
    • pydemo uses standard library's code and optparse modules. The latter is deprecated in Python 2.7 and replaced by argparse in Python 3.X.
    • Additional changes may be required related with encoding and how files are read.
  • To install the package you need setuptools or distribute. They are already installed from stock in several Linux flavours or in virtualenv, or you can download them from their PyPi page.
  • The installation script will try to install Pygments and readline as requirements. However, both packages are not mandatory, so you can remove them from the file requirements.txt and then proceed with the installation.
    • Let me remind that readline has some kind of incompatibilities with pip, so you better install it with easy_install beforehand.
  • In Windows the package will try to install only pyreadline, as Pygments does not work right with most usual command lines. If you use an advanced terminal you can edit requirements_win.txt to add Pygments (before installing).

Usage

$ pydemo --help
Usage: pydemo [--no-history] [--no-color] [--blanks NUM] [FILES]

Frappe Context Processor Backend process

Options:
  --version     show program's version number and exit
  -h, --help    show this help message and exit
  --blanks=NUM  Number of blank lines between each code block
  --no-history  Do not use or store history
  --no-color    Do not use colorful output

  • Use --blanks=NUM argument to specify minimum number of empty lines to take between each code block.

  • Use --no-history argument to not load or store the history (you will not be able to browse it inside the CLI).

  • Use --no-color to disable syntax highlight.

  • By default pydemo will take all the *.py files in the folder where you launch it, in alphabetical order.

  • When launched it prints a trace with information about files loaded:

$ pydemo
Loaded 1 files, 3 code blocks
...
  • You may provide a list of files to read instead. You may print the list of loaded files executing command %print_files:
$ pydemo tests/test3.py
Loaded 1 files, 5 code blocks
Python 2.7.2 (default, Oct 11 2012, 20:14:37)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(DemoHistoryConsole)
>>> %print_files
Loaded 1 files, 5 code blocks
In strict order:
    tests/test3.py
>>>
  • Each time you input an empty line a new code block is executed. You may interact with that code (e.g. access instances and class and functions declarations):
$ pydemo tests/test3.py
Loaded 1 files, 5 code blocks
Python 2.7.2 (default, Oct 11 2012, 20:14:37)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(DemoHistoryConsole)
>>>
#-*- coding: utf-8 -*-

>>>
class DemoClass(object):
    """Class to demonstrate pydemo
    """
    def __init__(self, val):
        """Constructor of the class
        """
        self.attr = val
    def power_attr(self, num):
        return num ** self.attr

>>>
inst = DemoClass(3)

>>> inst.attr
3
>>>
print inst.power_attr(2)
print inst.power_attr(3)
print inst.power_attr(4)

8
27
64
>>>
No more demo code available. Execute '%reload_files [FILENAMES]' to reload
  • Use %reload_files [FILENAMES] command to reload more files (more code blocks to execute):
$ pydemo tests/test3.py
Loaded 1 files, 5 code blocks
Python 2.7.2 (default, Oct 11 2012, 20:14:37)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(DemoHistoryConsole)
>>> %reload_files
Loaded 1 files, 5 code blocks
>>> %reload_files tests/test2.py
Loaded 1 files, 7 code blocks
>>>
  • Use %help command inside CLI to check the commands:
$ pydemo
Loaded 1 files, 3 code blocks
Python 2.7.2 (default, Oct 11 2012, 20:14:37)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
(DemoHistoryConsole)
>>> %help
pydemo (DemoHistoryConsole) help:

    %reload_files [FILENAMES] => Reload files. You must provide full or relative path. The extension '.py' is optional.

    %print_files              => Print currently loaded files.

Use exit() or Ctrl-D (i.e. EOF) to exit.

Wishlist

  • Support Windows
  • Support Python 3.X
  • Autocompletion
  • Use a generator to load files incrementally
  • Reload and reprocess files until current point (keep a "cursor")
  • Use iPython instead of code module
  • Implement web interface