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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>PythonCard Documentation: The Shell</title>
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<h1>PythonCard</h1>
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<div id="content">
<h2>Using the Shell in PythonCard</h2>
<p><strong>Version 1.2 of August 2, 2002</strong></p>
<p>PythonCard integrates a rich, high-level interactive Python shell. This
document describes how to launch and use this shell as you create PythonCard
applications. It is based on Version 0.6.5 of PythonCard.</p>
<p>The shell is based on the <a href="http://sourceforge.net/projects/pycrust">
PyCrust</a>
package created by Patrick O'Brien of Orbtech. The release of PyCrust
included with wxPython 2.3.2.1 is version 0.7. This document is based on
version 0.7.2 of PyCrust in cvs which you can get from SourceForge. This
newer version of PyCrust will be included with wxPython 2.3.3, expected out
sometime in May. There may be some features or key bindings described below
that are not available if you don't have the cvs version of PyCrust.</p>
<h3>Overview of Basic Shell Functionality</h3>
<p>In many ways, the PythonCard shell resembles IDLE, the Python editor
that is included in Python distributions. IDLE is Python's default editor.
But the PythonCard shell is more extensive and more robust both in its
editing capabilities and in its programming support than IDLE.</p>
<p>As you can see from Figure 1, the shell allows you to do interactive
programming at the standard Python prompt of three angle brackets
(">>>"). It behaves like IDLE, so there's nothing new to learn in
this respect.</p>
<p class="imageCaption"><img src="images/shellfig1.png" alt="PythonCard Shell" /><br />
Figure 1. Using PythonCard Shell as Interactive Programming Environment</p>
<p>Figure 1 also illustrates the shell's inclusion of syntax highlighting and
coloring. In its current release, it does not support customization of these
color highlights.</p>
<p>Pressing Enter anywhere on a line in the shell always processes the command
on that line if that line is the last one in the current editing window.
Pressing Enter on any other line copies that line's contents and places them
on the last line in the window, enabling you to execute the command again or
modify it slightly. This feature is quite valuable during testing when you
often type the same commands repeatedly. In Figure 2, we positioned the cursor
at the end of the line containing the simple statement "5+2" and
pressed Enter. Notice that 5+2 now appears as the last line in the editor.
Pressing Enter now produces the expected output of "7" on the next
line in the editor.</p>
<p class="imageCaption"><img src="images/shellfig2.png" alt="Copying commands in the shell" /><br />
Figure 2. Copying a Previous Command Line With Enter Key</p>
<p>You can use the ESCape key to change your mind about a line of Python code
you are entering that has not yet been executed bypressing Enter. This will
simply erase all the characters on the current line and return your cursor to
the Python prompt.</p>
<p>You can always obtain some basic help in the use of the shell by typing
"shell.help()" in the interactive editor area and pressing Enter.
The result will look something like Figure 3.</p>
<p class="imageCaption"><img src="images/shellfig3.png" alt="Help in the shell" /><br />
Figure 3. Result of Typing "shell.help()" in PythonCard Shell</p>
<p>The arrow keys navigate up, down, left and right in text displayed in the
shell, as you'd expect. Holding down the Alt key with the right or left arrow
moves the cursor by the rough equivalent of a "word" in the
direction of the arrow, with movement continuing across line boundaries.</p>
<p>By default, lines typed into the shell do not wrap. If you wish to see the
lines in your shell window wrap at the right border of the shell window,
type in the shell: shell.SetWrapMode(1). To turn it back off, type
shell.SetWrapMode(0).</p>
<h3>Key Bindings in the Shell</h3>
<p>Table 1 shows all of the key bindings defined in the PythonCard shell and
describes their usage.</p>
<p class="imageCaption">Table 1. Key Bindings in PythonCard Shell</p>
<table cellpadding="2" cellspacing="2" border="1" width="75%">
<tr>
<th>Key Combination</th>
<th>Usage</th>
</tr>
<tr>
<td>Home</td>
<td>Go to the beginning of the line</td>
</tr>
<tr>
<td>Shift + Home</td>
<td>Select from current cursor position to the beginning of the line</td>
</tr>
<tr>
<td>End</td>
<td>Go to the end of the line</td>
</tr>
<tr>
<td>Shift + End</td>
<td>Select from the current cursor position to the end of the line</td>
</tr>
<tr>
<td>Alt + Right Arrow</td>
<td>Move cursor to the right roughly by a word</td>
</tr>
<tr>
<td>Alt + Left Arrow</td>
<td>Move cursor to the left roughly by a word</td>
</tr>
<tr>
<td>Ctrl + C</td>
<td>Copy the selection to the clipboard</td>
</tr>
<tr>
<td>Ctrl + Shift + C</td>
<td>Copy the selection including the prompts, if any, to the clipboard</td>
</tr>
<tr>
<td>Ctrl + X</td>
<td>Cut the selection to the clipboard</td>
</tr>
<tr>
<td>Ctrl + V</td>
<td>Paste the clipboard contents at the cursor location</td>
</tr>
<tr>
<td>Ctrl + Shift + V</td>
<td>Paste the current multi-line clipboard contents at the cursor location</td>
</tr>
<tr>
<td>Ctrl + Up Arrow</td>
<td>Retrieve most recent History item</td>
</tr>
<tr>
<td>Ctrl + Enter</td>
<td>Inserts a blank line between existing lines in a multiline command.</td>
</tr>
<tr>
<td>Alt + P</td>
<td>Retrieve most recent History item</td>
</tr>
<tr>
<td>Ctrl + Down Arrow</td>
<td>Retrieve next History item in the queue</td>
</tr>
<tr>
<td>Alt + N</td>
<td>Retrieve next History item in the queue</td>
</tr>
<tr>
<td>Shift + Up Arrow</td>
<td>Retrieve previous History item</td>
</tr>
<tr>
<td>Shift + Down Arrow</td>
<td>Retrieve next History item in the queue</td>
</tr>
<tr>
<td>F8</td>
<td>Retrieve a specific History item by typing its first few characters and then pressing F8</td>
</tr>
</table>
<h3>Auto-Completion in the Shell</h3>
<p>One of the biggest time-saving features built into the PythonCard shell is
auto-completion. Whenever you type a period in identifying a Python or
PythonCard object, method, or property, the shell displays a popup menu with
all of the legal completions to that statement that the shell knows about.
For example, in Figure 4, we imported the standard "os" module and
then typed "os" followed by a period. The popup menu shown in the
figure appears.</p>
<p class="imageCaption"><img src="images/shellfig4.png" alt="Shell with pop-up" /><br />
Figure 4. Auto-CompletionPopup Menu</p>
<p>There are three ways to find the text you wish to type to complete this
portion of the descriptor:</p>
<ol>
<li>You can keep typing. The popup menu uses incremental search to keep
scrolling to the next string that matches what you are typing.</li>
<li>You can scroll the popup menu with the mouse in the usual way and
select the proper completion string.</li>
<li>You can use the arrow keys to move around inside the popup menu and
select the proper completion string.</li>
</ol>
<p>Once you have selected the completion string you want, you can press Enter
or the Tab key to insert it into the text at the insertion point.</p>
<p>If the auto-completion menu gets in your way, you can click anywhere
outside its boundaries or simply press the ESCape key to close it.</p>
<p>You can turn this auto-completion feature on and off by typing appropriate
commands in the shell. To turn the feature on, type in the shell:</p>
<p class="code">shell.autoComplete = 1</p>
<p>To turn the feature off, substitute a zero in the above command.</p>
<p>Special Python attributes are prefixed with underscore characters. Some
of these attributes use only a single underscore while others use two. You
can include or exclude each of these types of attributes in the
auto-completion list that appears in the shell by setting two different
variables: autoCompleteIncludeSingle and autoCompleteIncludeDouble. For
example, to exclude attributes preceded by single underscores from the list,
type:</p>
<p class="code">shell.autoCompleteIncludeSingle = 0</p>
<p>Similarly, setting autoCompleteIncludeSingle to a value of 1 will include
those attributes. The same is true for the autoCompleteIncludeDouble
setting.</p>
<p>Python objects include another type of attribute, often referred to as
"magic attributes." These attributes' values can only be obtained
by calling the object's _getAttributeNames() method, if it has one. You can
determine whether these attributes are included in the auto-completion popup
by setting the variable autoCompleteIncludeMagic to 1 to include them, 0 to
exclude them:</p>
<p class="code">shell.autoCompleteIncludeMagic = 1</p>
<h3>Documentation Auto-Display in the Shell</h3>
<p>Similarly to the auto-completion popup described in the preceding section,
the PythonCard shell also includes the ability to automatically display
important documentation for any function or method. Simply type the method
or function name and the opening (left) parenthesis and the shell displays
helpful information describing the function. These "call tips"
attempt to display on their first line all of the arguments expected by a
callable object. Where the object involved is the class name, the arguments
expected by the class constructor are displayed. The second line of the call
tip displays the docstring for the object if it has one.</p>
<p>Figure 5 demonstrates this feature. We have typed "os.fdopen("
and the resulting tool tip tells us the required and optional parameters and
what the function does as well as what it returns.</p>
<p class="imageCaption"><img src="images/shellfig5.png" alt="Tool tips in the shell" /><br />
Figure 5. Tool Tip Shows Documentation String While Typing Functions and Methods</p>
<p>Virtually all of PythonCard's built-in functions and methods have
docstrings associated with them or will have prior to the final release of
the product.</p>
<h3>Editing and Retrieving Functions and Compound Statements in the Shell</h3>
<p>You can copy, paste, edit, and execute multi-line functions and compound
statements in the PythonCard shell. This can be a huge time-saver when you
want to re-execute a method you've defined in the interactive editor. To do
so, simply use any of the history retrieval methods outlined in Table 1 to
copy any group of multiple lines and then edit them in place. If you, e.g.,
define a function or class in the shell and you make a mistake, you can avoid
the usually mandatory complete re-typing of the code by copying the whole
thing and then editing the mistakes. You can also use the PythonCard shell
in conjunction with another Python-aware editor. You could, e.g., create a
class in another editor, then copy its definition and paste it into the shell
to experiment with it. Each time you need a new copy of the class definition,
simply paste it again.</p>
<p>You may find yourself occasionally wanting to re-execute multiple
<em>commands</em> , each of which may be a single line or a multi-line
command. In that situation, pasting those lines into the shell using
Shift+Ctrl+V will paste all the lines and run all of the commands contained
in the selection.</p>
<p>If you want to copy multi-line commands from the shell into another file
(e.g., for documentation purposes), you can select and then use Ctrl+C to
copy those lines. This will strip the Python shell prompts out of the copied
material. If, however, you wish to <em>retain</em> those prompts, use
Shift+Ctrl+C to perform the copy and the prompts will be preserved when you
paste the selection into another window or file.</p>
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<p>$Revision: 1.5 $ : $Author: kasplat $ : Last updated $Date: 2004/07/26 15:35:31 $</p>
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