# The wxPython Manual

## A guide to wxPython for Python programmers

Author: | Patrick K. O'Brien
Contact: | pobrien@orbtech.com
Organization: | Orbtech
Date: | 2004-03-26
Revision: | 26380
License: | wxWindows Free Documentation Licence, Version 3

Contents

- Introduction
- What is wxPython?
- wxPython requirements
  - MS-Windows
  - Linux or Unix
  - Mac OS X
- What is wxWidgets?
- Why another cross-platform development tool?
- wxPython Overview
- Utilities and libraries supplied with wxPython
- Creating and deleting wxPython objects
- App overview
  - Application initialization
  - Application shutdown
- Sizer overview
  - The idea behind sizers
  - Common features
    - A minimal size
    - A border
    - An alignment
    - A stretch factor
  - BoxSizer
  - StaticBoxSizer
  - GridSizer
  - FlexGridSizer
  - NotebookSizer
  - Programming with BoxSizer
  - Programming with GridSizer
  - Programming with FlexGridSizer
  - Programming with NotebookSizer
  - Programming with StaticBoxSizer
  - Dialog.CreateButtonSizer
- Date and time classes overview
  - All date/time classes at a glance
  - DateTime characteristics
  - Difference between DateSpan and TimeSpan
  - Date arithmetics
  - Time zone considerations
  - Daylight saving time (DST)
  - DateTime and Holidays
- Classes by category
- ID constants
- Source document
- Submitting changes to the source document
- Contributors
- License

# Introduction

This is a guide to the wxPython GUI toolkit, written by a Python programmer for his fellow Python programmers. It began as a simple translation of the wxWidgets documentation (which is written for C++ programmers), and evolved from there. And while there's nothing wrong with C++...

Okay, you got me there. I hate C++. That's why I use Python. If you like C++, go read the wxWidgets documentation. If you'd rather read a guide that's written with Python programmers in mind, keep reading this one. If you like it, feel free to send me freshly roasted coffee beans, dark chocolate, and large denomination currency. Better yet, buy huge quantities of my wxPython book (written with Robin Dunn) and send one to each of your friends, relatives, and coworkers.

# What is wxPython?

wxPython is a GUI toolkit for the Python programming language. It allows Python programmers to create programs with a robust, highly functional graphical user interface, simply and easily. It is implemented as a Python extension module (native code) that wraps the popular wxWidgets cross platform GUI library, which is written in C++.

Like Python and wxWidgets, wxPython is Open Source, which means that it is free for anyone to use and the source code is available for anyone to look at and modify. And anyone can contribute fixes or enhnacments to the project.

wxPython is a cross-platform toolkit. This means that the same program will run on multiple platforms without modification. Currently supported platforms are 32-bit Microsoft Windows, most Unix or unix-like systems, and Macintosh OS X.

Since the language is Python, wxPython programs are simple, easy to write and easy to understand.

# wxPython requirements

To make use of wxPython, you currently need one of the following setups.

## MS-Windows

- A 486 or higher PC running MS Windows.
- At least ?? MB of disk space.

## Linux or Unix

- Almost any C++ compiler, including GNU C++ (EGCS 1.1.1 or above).
- Almost any Unix workstation, and one of: GTK+ 1.2, GTK+ 2.0, Motif 1.2 or higher, Lesstif.
- At least ?? MB of disk space.

## Mac OS X

- A PowerPC Mac running Mac OS X 10.x.
- At least ?? MB of disk space.

# What is wxWidgets?

wxWidgets is a C++ framework providing GUI (Graphical User Interface) and other facilities on more than one platform. Version 2 currently supports all desktop versions of MS Windows, Unix with GTK+, Unix with Motif, and MacOS. An OS/2 port is in progress.

wxWidgets was originally developed at the Artificial Intelligence Applications Institute, University of Edinburgh, for internal use, and was first made publicly available in 1992. Version 2 is a vastly improved version written and maintained by Julian Smart, Robert Roebling, Vadim Zeitlin, Vaclav Slavik and many others.

Please note that in the following, "MS Windows" often refers to all platforms related to Microsoft Windows, including 16-bit and 32-bit variants, unless otherwise stated. All trademarks are acknowledged.

# Why another cross-platform development tool?

wxWidgets was developed to provide a cheap and flexible way to maximize investment in GUI application development. While a number of commercial class libraries already existed for cross-platform development, none met all of the following criteria:

- low price
- source availability
- simplicity of programming
- support for a wide range of compilers

Since wxWidgets was started, several other free or almost-free GUI frameworks have emerged. However, none has the range of features, flexibility, documentation and the well-established development team that wxWidgets has.

As open source software, wxWidgets has benefited from comments, ideas, bug fixes, enhancements and the sheer enthusiasm of users. This gives wxWidgets a certain advantage over its commercial competitors (and over free libraries without an independent development team), plus a robustness against the transience of one individual or company. This openness and availability of source code is especially important when the future of thousands of lines of application code may depend upon the longevity of the underlying class library.

Version 2 goes much further than previous versions in terms of generality and features, allowing applications to be produced that are often indistinguishable from those produced using single-platform toolkits such as Motif, GTK+ and MFC.

The importance of using a platform-independent class library cannot be overstated, since GUI application development is very time-consuming, and sustained popularity of particular GUIs cannot be guaranteed. Code can very quickly become obsolete if it addresses the wrong platform or audience. wxWidgets helps to insulate the programmer from these winds of change. Although wxWidgets may not be suitable for every application (such as an OLE-intensive program), it provides access to most of the functionality a GUI program normally requires, plus many extras such as network programming, PostScript output, and HTML rendering; and it can of course be extended as needs dictate. As a bonus, it provides a far cleaner and easier programming interface than the native APIs. Programmers may find it worthwhile to use wxWidgets even if they are developing on only one platform.

It is impossible to sum up the functionality of wxWidgets in a few paragraphs, but here are some of the benefits:

- Low cost (free, in fact!)
- You get the source.
- Available on a variety of popular platforms.
- Works with almost all popular C++ compilers and Python.
- Over 50 example programs.
- Over 1000 pages of printable and on-line documentation.
- Includes Tex2RTF, to allow you to produce your own documentation in Windows Help, HTML and Word RTF formats.
- Simple-to-use, object-oriented API.
- Flexible event system.
- Graphics calls include lines, rounded rectangles, splines, polylines, etc.
- Constraint-based and sizer-based layouts.
- Print/preview and document/view architectures.
- Toolbar, notebook, tree control, advanced list control classes.
- PostScript generation under Unix, normal MS Windows printing on the PC.
- MDI (Multiple Document Interface) support.
- Can be used to create DLLs under Windows, dynamic libraries on Unix.
- Common dialogs for file browsing, printing, colour selection, etc.
- Under MS Windows, support for creating metafiles and copying them to the clipboard.
- An API for invoking help from applications.
- Ready-to-use HTML window (supporting a subset of HTML).
- Dialog Editor for building dialogs.
- Network support via a family of socket and protocol classes.
- Support for platform independent image processing.
- Built-in support for many file formats (BMP, PNG, JPEG, GIF, XPM, PNM, PCX).

# wxPython Overview

To set a wxPython application going, you will need to derive an App class and override App.OnInit.

An application must have a top-level Frame or Dialog window. Each frame may contain one or more instances of classes such as Panel, SplitterWindow or other windows and controls.

A frame can have a MenuBar, a ToolBar, a status line, and an Icon for when the frame is iconized.

A Panel is used to place controls (classes derived from Control) which are used for user interaction. Examples of controls are Button, CheckBox, Choice, ListBox, RadioBox, Slider.

Instances of Dialog can also be used for controls, and they have the advantage of not requiring a separate frame.

Instead of creating a dialog box and populating it with items, it is possible to choose one of the convenient common dialog classes, such as MessageDialog and FileDialog.

You never draw directly onto a window. Instead, you use a device context (DC). DC is the base for ClientDC, PaintDC, MemoryDC, PostScriptDC, MemoryDC, MetafileDC and PrinterDC. If your drawing functions have DC as a parameter, you can pass any of these DCs to the function, and thus use the same code to draw to several different devices. You can draw using the member functions of DC, such as DC.DrawLine and DC.DrawText. Control colour on a window (Colour) with brushes (Brush) and pens (Pen).

Most modern applications will have an on-line, hypertext help system; for this, you need Help and the HelpController class to control Help.

GUI applications aren't all graphical wizardry. You'll also need lists and hash tables. But since you're working with Python, you should use the ones Python provides (list, tuple, dict), rather than the wxWidgets versions. Same goes for the database related classes. The basic rule of thumb is this: If you can do it directly in Python, you probably should. If there is a reason not to use a Python data type, wxPython will provide a wrapper for the wxWidgets class.

You will undoubtedly need some platform-independent file functions, and you may find it handy to maintain and search a list of paths using PathList. There's a miscellany of operating system and other functions.

See also Classes by Category for a list of classes.

# Utilities and libraries supplied with wxPython

In addition to the core wxWidgets library, a number of further libraries and utilities are supplied with each distribution.

[Need to list these.]

# Creating and deleting wxPython objects

[This section needs to be reviewed.]

# App overview

Classes: wx.App

## Application initialization

The OnInit method defined for a class derived from wx.App will usually create a top window as a bare minimum.

OnInit must return a boolean value to indicate whether processing should continue (True) or not (False). You call App.SetTopWindow to let wxPython know about the top window.

An application closes by destroying all windows. Because all frames must be destroyed for the application to exit, it is advisable to use parent frames wherever possible when creating new frames, so that deleting the top level frame will automatically delete child frames. The alternative is to explicitly delete child frames in the top-level frame's CloseEvent handler.

In emergencies the wx.Exit() function can be called to kill the application, however, normally the application shuts down automatically, see below.

An example of defining an application follows:

    import wx

    from frame import Frame

    class App(wx.App):
        """Application class."""

        def OnInit(self):
            self.frame = Frame()
            self.frame.Show()
            self.SetTopWindow(self.frame)
            return True

    def main():
        app = App()
        app.MainLoop()

    if __name__ == '__main__':
        main()

## Application shutdown

The application normally shuts down when the last of its top level windows is closed. This is normally the expected behaviour and means that it is enough to call Close() in response to the "Exit" menu command if your program has a single top level window. If this behaviour is not desirable, App.SetExitOnFrameDelete can be called to change it. Note that such logic doesn't apply for the windows shown before the program enters the main loop: in other words, you can safely show a dialog from App.OnInit and not be afraid that your application terminates when this dialog -- which is the last top level window for the moment -- is closed.

Another aspect of the application shutdown is the OnExit which is called when the application exits but before wxPython cleans up its internal structures. You should delete all wxPython objects that you created by the time OnExit finishes.

For example, this code may crash:

[Need examples of objects needing cleanup to keep app from crashing.]

# Sizer overview

Classes: wx.Sizer, wx.GridSizer, wx.FlexGridSizer, wx.BoxSizer, wx.StaticBoxSizer, wx.NotebookSizer, wx.CreateButtonSizer

Sizer | Abstract base class.
GridSizer | A sizer for laying out windows in a grid with all fields having the same size.
FlexGridSizer | A sizer for laying out windows in a flexible grid.
BoxSizer | A sizer for laying out windows in a row or column.
StaticBoxSizer | Same as BoxSizer, but with a surrounding static box.
NotebookSizer | Sizer to use with the Notebook control.

Sizers, as represented by the wx.Sizer class and its descendants in the wxPython class hierarchy, have become the method of choice to define the layout of controls in dialogs in wxPython because of their ability to create visually appealing dialogs independent of the platform, taking into account the differences in size and style of the individual controls. Editors such as wxDesigner, wxrcedit, XRCed and wxWorkshop create dialogs based exclusively on sizers, practically forcing the user to create platform independent layouts without compromises.

## The idea behind sizers

The layout algorithm used by sizers in wxPython is closely related to layout systems in other GUI toolkits, such as Java's AWT, the GTK toolkit or the Qt toolkit. It is based upon the idea of individual subwindows reporting their minimal required size and their ability to get stretched if the size of the parent window has changed. This will most often mean that the programmer does not set the start-up size of a dialog, the dialog will rather be assigned a sizer and this sizer will be queried about the recommended size. This sizer in turn will query its children (which can be normal windows, empty space or other sizers) so that a hierarchy of sizers can be constructed. Note that wx.Sizer does not derive from wx.Window and thus does not interfere with tab ordering and requires very few resources compared to a real window on screen.

What makes sizers so well fitted for use in wxPython is the fact that every control reports its own minimal size and the algorithm can handle differences in font sizes or different window (dialog item) sizes on different platforms without problems. For example, if the standard font as well as the overall design of Linux/GTK widgets requires more space than on Windows, the initial dialog size will automatically be bigger on Linux/GTK than on Windows.

There are currently five different kinds of sizers available in wxPython. Each represents either a certain way to lay out dialog items in a dialog or it fulfils a special task such as wrapping a static box around a dialog item (or another sizer). These sizers will be discussed one by one in the text below.

## Common features

All sizers are containers, that is, they are used to lay out one dialog item (or several dialog items), which they contain. Such items are sometimes referred to as the children of the sizer. Independent of how the individual sizers lay out their children, all children have certain features in common:

### A minimal size

This minimal size is usually identical to the initial size of the controls and may either be set explicitly in the size field of the control constructor or may be calculated by wxPython, typically by setting the height and/or the width of the item to -1. Note that only some controls can calculate their size (such as a checkbox) whereas others (such as a listbox) don't have any natural width or height and thus require an explicit size. Some controls can calculate their height, but not their width (e.g. a single line text control):

[Need graphics]

### A border

The border is just empty space and is used to separate dialog items in a dialog. This border can either be all around, or at any combination of sides such as only above and below the control. The thickness of this border must be set explicitly, typically 5 points. The following samples show dialogs with only one dialog item (a button) and a border of 0, 5, and 10 pixels around the button:

[Need graphics]

### An alignment

Often, a dialog item is given more space than its minimal size plus its border. Depending on what flags are used for the respective dialog item, the dialog item can be made to fill out the available space entirely, i.e. it will grow to a size larger than the minimal size, or it will be moved to either the centre of the available space or to either side of the space. The following sample shows a listbox and three buttons in a horizontal box sizer; one button is centred, one is aligned at the top, one is aligned at the bottom:

[Need graphics]

### A stretch factor

If a sizer contains more than one child and it is offered more space than its children and their borders need, the question arises how to distribute the surplus space among the children. For this purpose, a stretch factor may be assigned to each child, where the default value of 0 indicates that the child will not get more space than its requested minimum size. A value of more than zero is interpreted in relation to the sum of all stretch factors in the children of the respective sizer, i.e. if two children get a stretch factor of 1, they will get half the extra space each independent of whether one control has a minimal sizer inferior to the other or not. The following sample shows a dialog with three buttons, the first one has a stretch factor of 1 and thus gets stretched, whereas the other two buttons have a stretch factor of zero and keep their initial width:

[Need graphics]

Within wxDesigner, this stretch factor gets set from the Option menu.

## BoxSizer

BoxSizer can lay out its children either vertically or horizontally, depending on what flag is being used in its constructor. When using a vertical sizer, each child can be centered, aligned to the right or aligned to the left. Correspondingly, when using a horizontal sizer, each child can be centered, aligned at the bottom or aligned at the top. The stretch factor described in the last paragraph is used for the main orientation, i.e. when using a horizontal box sizer, the stretch factor determines how much the child can be stretched horizontally. The following sample shows the same dialog as in the last sample, only the box sizer is a vertical box sizer now:

[Need graphics]

## StaticBoxSizer

StaticBoxSixer is the same as a BoxSizer, but surrounded by a static box. Here is a sample:

[Need graphics]

## GridSizer

GridSizer is a two-dimensional sizer. All children are given the same size, which is the minimal size required by the biggest child, in this case the text control in the left bottom border. Either the number of columns or the number or rows is fixed and the grid sizer will grow in the respectively other orientation if new children are added:

[Need graphics]

## FlexGridSizer

Another two-dimensional sizer derived from GridSizer. The width of each column and the height of each row are calculated individually according the minimal requirements from the respectively biggest child. Additionally, columns and rows can be declared to be stretchable if the sizer is assigned a size different from that which it requested. The following sample shows the same dialog as the one above, but using a flex grid sizer:

[Need graphics]

## NotebookSizer

NotebookSizer can be used with notebooks. It calculates the size of each notebook page and sets the size of the notebook to the size of the biggest page plus some extra space required for the notebook tabs and decorations.

[Need graphics]

## Programming with BoxSizer

The basic idea behind a BoxSizer is that windows will most often be laid out in rather simple basic geometry, typically in a row or a column or several hierarchies of either.

As an example, we will construct a dialog that will contain a text field at the top and two buttons at the bottom. This can be seen as a top-hierarchy column with the text at the top and buttons at the bottom and a low-hierarchy row with an OK button to the left and a Cancel button to the right. In many cases (particularly dialogs under Unix and normal frames) the main window will be resizable by the user and this change of size will have to get propagated to its children. In our case, we want the text area to grow with the dialog, whereas the button shall have a fixed size. In addition, there will be a thin border around all controls to make the dialog look nice and - to make matter worse - the buttons shall be centred as the width of the dialog changes.

It is the unique feature of a box sizer, that it can grow in both directions (height and width) but can distribute its growth in the main direction (horizontal for a row) unevenly among its children. In our example case, the vertical sizer is supposed to propagate all its height changes to only the text area, not to the button area. This is determined by the proportion parameter when adding a window (or another sizer) to a sizer. It is interpreted as a weight factor, i.e. it can be zero, indicating that the window may not be resized at all, or above zero. If several windows have a value above zero, the value is interpreted relative to the sum of all weight factors of the sizer, so when adding two windows with a value of 1, they will both get resized equally much and each half as much as the sizer owning them.

Then what do we do when a column sizer changes its width? This behaviour is controlled by flags (the second parameter of the Add() function): zero or no flag indicates that the window will preserve it is original size, wx.GROW flag (same as wx.EXPAND) forces the window to grow with the sizer, and wx.SHAPED flag tells the window to change it is size proportionally, preserving original aspect ratio. When wx.GROW flag is not used, the item can be aligned within available space. wx.ALIGN_LEFT, wx.ALIGN_TOP, wx.ALIGN_RIGHT, wx.ALIGN_BOTTOM, wx.ALIGN_CENTER_HORIZONTAL and wx.ALIGN_CENTER_VERTICAL do what they say. wx.ALIGN_CENTRE (same as wx.ALIGN_CENTER) is defined as (`wx.ALIGN_CENTER_HORIZONTAL | wx.ALIGN_CENTER_VERTICAL`). Default alignment is `wx.ALIGN_LEFT | wx.ALIGN_TOP`.

As mentioned above, any window belonging to a sizer may have border, and it can be specified which of the four sides may have this border, using the wx.TOP, wx.LEFT, wx.RIGHT and wx.BOTTOM constants or wx.ALL for all directions (and you may also use wx.NORTH, wx.WEST etc instead). These flags can be used in combination with the alignment flags above as the second parameter of the Add() method using the binary or operator (`|`). The sizer of the border also must be made known, and it is the third parameter in the Add() method. This means, that the entire behaviour of a sizer and its children can be controlled by the three parameters of the Add() method.

[Show code and graphic here.]

## Programming with GridSizer

GridSizer is a sizer which lays out its children in a two-dimensional table with all table fields having the same size, i.e. the width of each field is the width of the widest child, the height of each field is the height of the tallest child.

[Show code and graphic here.]

## Programming with FlexGridSizer

FlexGridSizer is a sizer which lays out its children in a two-dimensional table with all table fields in one row having the same height and all fields in one column having the same width, but all rows or all columns are not necessarily the same height or width as in the GridSizer.

[Show code and graphic here.]

## Programming with NotebookSizer

NotebookSizer is a specialized sizer to make sizers work in connection with using notebooks. This sizer is different from any other sizer as you must not add any children to it - instead, it queries the notebook class itself. The only thing this sizer does is to determine the size of the biggest page of the notebook and report an adjusted minimal size to a more toplevel sizer.

In order to query the size of notebook page, this page needs to have its own sizer, otherwise the NotebookSizer will ignore it. Notebook pages get their sizer by assigning one to them using SetSizer() and setting the auto-layout option to True using SetAutoLayout(). Here is one example showing how to add a notebook page that the notebook sizer is aware of:

[Show code and graphic here.]

## Programming with StaticBoxSizer

StaticBoxSizer is a sizer derived from BoxSizer but adds a static box around the sizer. Note that this static box has to be created separately.

[Show code and graphic here.]

## Dialog.CreateButtonSizer

As a convenience, the Dialog class has a CreateButtonSizer(flags) method that can be used to create a standard button sizer in which standard buttons are displayed. The following flags can be passed to this method:

wx.YES_NO | add Yes/No subpanel
wx.YES | return wx.ID_YES
wx.NO | return wx.ID_NO
wx.NO_DEFAULT | make the wx.NO button the default, otherwise wx.YES or wx.OK button will be default
wx.OK | return wx.ID_OK
wx.CANCEL | return wx.ID_CANCEL
wx.HELP | return wx.ID_HELP
wx.FORWARD | return wx.ID_FORWARD
wx.BACKWARD | return wx.ID_BACKWARD
wx.SETUP | return wx.ID_SETUP
wx.MORE | return wx.ID_MORE

# Date and time classes overview

wxPython provides a set of powerful classes to work with dates and times. Some of the supported features of the DateTime class are:

Wide range | The range of supported dates goes from about 4714 B.C. to some 480 million years in the future.
Precision | Not using floating point calculations anywhere ensures that the date calculations don't suffer from rounding errors.
Many features | Not only all usual calculations with dates are supported, but also more exotic week and year day calculations, work day testing, standard astronomical functions, conversion to and from strings in either strict or free format.
Efficiency | Objects of DateTime are small (8 bytes) and working with them is fast

## All date/time classes at a glance

There are 3 main classes: except DateTime itself which represents an absolute moment in time, there are also two classes - TimeSpan and DateSpan which represent the intervals of time.

There are also helper classes which are used together with DateTime: DateTimeHolidayAuthority which is used to determine whether a given date is a holiday or not and DateTimeWorkDays which is a derivation of this class for which (only) Saturdays and Sundays are the holidays. See more about these classes in the discussion of the holidays.

## DateTime characteristics

DateTime stores the time as a signed number of milliseconds since the Epoch which is fixed, by convention, to Jan 1, 1970 - however this is not visible to the class users (in particular, dates prior to the Epoch are handled just as well (or as bad) as the dates after it). But it does mean that the best resolution which can be achieved with this class is 1 millisecond.

The size of DateTime object is 8 bytes because it is represented as a 64 bit integer. The resulting range of supported dates is thus approximatively 580 million years, but due to the current limitations in the Gregorian calendar support, only dates from Nov 24, 4714BC are supported (this is subject to change if there is sufficient interest in doing it).

Finally, the internal representation is time zone independent (always in GMT) and the time zones only come into play when a date is broken into year/month/day components. See more about timezones below.

Currently, the only supported calendar is Gregorian one (which is used even for the dates prior to the historic introduction of this calendar which was first done on Oct 15, 1582 but is, generally speaking, country, and even region, dependent). Future versions will probably have Julian calendar support as well and support for other calendars (Maya, Hebrew, Chinese...) is not ruled out.

## Difference between DateSpan and TimeSpan

While there is only one logical way to represent an absolute moment in the time (and hence only one DateTime class), there are at least two methods to describe a time interval.

First, there is the direct and self-explaining way implemented by TimeSpan: it is just a difference in milliseconds between two moments in time. Adding or subtracting such an interval to DateTime is always well-defined and is a fast operation.

But in daily life other, calendar-dependent time interval specifications are used. For example, 'one month later' is commonly used. However, it is clear that this is not the same as TimeSpan of 60*60*24*31 seconds because 'one month later' Feb 15 is Mar 15 and not Mar 17 or Mar 16 (depending on whether the year is leap or not).

This is why there is another class for representing such intervals called DateSpan. It handles these sort of operations in the most natural way possible, but note that manipulating with intervals of this kind is not always well-defined. Consider, for example, Jan 31 + '1 month': this will give Feb 28 (or 29), i.e. the last day of February and not the non-existent Feb 31. Of course, this is what is usually wanted, but you still might be surprised to notice that now subtracting back the same interval from Feb 28 will result in Jan 28 and not Jan 31 we started with!

So, unless you plan to implement some kind of natural language parsing in the program, you should probably use TimeSpan instead of DateSpan (which is also more efficient). However, DateSpan may be very useful in situations when you do need to understand what 'in a month' means (of course, it is just DateTime.Now() + DateSpan.Month()).

## Date arithmetics

Many different operations may be performed with the dates, however not all of them make sense. For example, multiplying a date by a number is an invalid operation, even though multiplying either of the time span classes by a number is perfectly valid.

Here is what can be done:

Addition | a TimeSpan or DateSpan can be added to DateTime resulting in a new DateTime object and also 2 objects of the same span class can be added together giving another object of the same class.
Subtraction | the same types of operations as above are allowed and, additionally, a difference between two DateTime objects can be taken and this will yield TimeSpan.
Multiplication | a TimeSpan or DateSpan object can be multiplied by an integer number resulting in an object of the same type.
Unary minus | a TimeSpan or DateSpan object may finally be negated giving an interval of the same magnitude but of opposite time direction.

## Time zone considerations

Although the time is always stored internally in GMT, you will usually work in the local time zone. Because of this, all DateTime constructors and setters which take the broken down date assume that these values are for the local time zone. Thus, DateTime(1, DateTime.Jan, 1970) will not correspond to the DateTime Epoch unless you happen to live in the UK.

All methods returning the date components (year, month, day, hour, minute, second...) will also return the correct values for the local time zone by default. So, generally, doing the natural things will lead to natural and correct results.

If you only want to do this, you may safely skip the rest of this section. However, if you want to work with different time zones, you should read it to the end.

In this (rare) case, you are still limited to the local time zone when constructing DateTime objects, i.e. there is no way to construct a DateTime corresponding to the given date in, say, Pacific Standard Time. To do it, you will need to call ToTimezone or MakeTimezone methods to adjust the date for the target time zone. There are also special versions of these functions ToGMT and MakeGMT for the most common case - when the date should be constructed in GMT.

You also can just retrieve the value for some time zone without converting the object to it first. For this you may pass TimeZone argument to any of the methods which are affected by the time zone (all methods getting date components and the date formatting ones, for example). In particular, the Format() family of methods accepts a TimeZone parameter and this allows to simply print time in any time zone.

To see how to do it, the last issue to address is how to construct a TimeZone object which must be passed to all these methods. First of all, you may construct it manually by specifying the time zone offset in seconds from GMT, but usually you will just use one of the symbolic time zone names and let the conversion constructor do the job. I.e. you would just write

wxDateTime dt(...whatever...); printf("The time is %s in local time zone", dt.FormatTime().c_str()); printf("The time is %s in GMT", dt.FormatTime(wxDateTime::GMT).c_str());

## Daylight saving time (DST)

DST (a.k.a. 'summer time') handling is always a delicate task which is better left to the operating system which is supposed to be configured by the administrator to behave correctly. Unfortunately, when doing calculations with date outside of the range supported by the standard library, we are forced to deal with these issues ourselves.

Several functions are provided to calculate the beginning and end of DST in the given year and to determine whether it is in effect at the given moment or not, but they should not be considered as absolutely correct because, first of all, they only work more or less correctly for only a handful of countries (any information about other ones appreciated!) and even for them the rules may perfectly well change in the future.

The time zone handling methods use these functions too, so they are subject to the same limitations.

## DateTime and Holidays

[TODO]

# Classes by category

Not done yet.

# ID constants

wxPython provides the following predefined ID constants:

ID_ABORT ID_ABOUT ID_ANY ID_APPLY ID_BACKWARD ID_CANCEL ID_CLEAR ID_CLOSE ID_CLOSE_ALL ID_CONTEXT_HELP ID_COPY ID_CUT ID_DEFAULT ID_DUPLICATE ID_EXIT ID_FILE1 ID_FILE2 ID_FILE3 ID_FILE4 ID_FILE5 ID_FILE6 ID_FILE7 ID_FILE8 ID_FILE9 ID_FILTERLISTCTRL ID_FIND ID_FORWARD ID_HELP ID_HELP_COMMANDS ID_HELP_CONTENTS ID_HELP_CONTEXT ID_HELP_PROCEDURES ID_IGNORE ID_MORE ID_NEW ID_NO ID_NOTOALL ID_OK ID_OPEN ID_PASTE ID_PREVIEW ID_PRINT ID_PRINT_SETUP ID_REDO ID_RESET ID_RETRY ID_REVERT ID_SAVE ID_SAVEAS ID_SELECTALL ID_SEPARATOR ID_SETUP ID_STATIC ID_TREECTRL ID_UNDO ID_YES ID_YESTOALL

# Source document

The source document is named wxPythonManual.txt and can be found by clicking the link at the bottom of this page (assuming you are viewing the html file). It is written using a fantastic formatting convention called reStructuredText. The wxPythonManual.html file is created using the Docutils utilities, which can turn reStructuredText documents into html, xml, pdf, and even OpenOffice files.

# Submitting changes to the source document

Some items in the source text file look like this:

    .. This is text from the wxWidgets documentation that needs to be
       translated into something appropriate for the wxPython version.
       The two dots followed by uniformly indented text turns this
       paragraph into a reStructuredText comment, so it doesn't appear
       in any output file, such as the html file.

They have been commented out and are awaiting editorial review and a rewrite so that they make sense in the context of wxPython. Feel free to send me suggestions for rewording these, or any other parts of this document that you think need improving. I will be eternally grateful to you and will show my gratitude by adding your name to the list of contributors. (Contributors who also send me gifts of coffee, chocolate, or currency will have their names listed in bold.)

# Contributors

Individuals who contributed to this documentation (in order by last name):

- Robin Dunn
- Patrick K. O'Brien
- Robert Roebling
- Julian Smart
- Vadim Zeitlin

# License

This document began as a translation of the wxWidgets documentation. As such, it adheres to the same license, which is provided here:

                    wxWindows Free Documentation Licence, Version 3
                    ===============================================

      Copyright (c) 1998 Julian Smart, Robert Roebling et al

      Everyone is permitted to copy and distribute verbatim copies
      of this licence document, but changing it is not allowed.

                       WXWINDOWS FREE DOCUMENTATION LICENCE
         TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

      1. Permission is granted to make and distribute verbatim copies of this
      manual or piece of documentation provided any copyright notice and this
      permission notice are preserved on all copies.

      2. Permission is granted to process this file or document through a
      document processing system and, at your option and the option of any third
      party, print the results, provided a printed document carries a copying
      permission notice identical to this one.

      3. Permission is granted to copy and distribute modified versions of this
      manual or piece of documentation under the conditions for verbatim
      copying, provided also that any sections describing licensing conditions
      for this manual, such as, in particular, the GNU General Public Licence,
      the GNU Library General Public Licence, and any wxWindows Licence are
      included exactly as in the original, and provided that the entire
      resulting derived work is distributed under the terms of a permission
      notice identical to this one.

      4. Permission is granted to copy and distribute translations of this
      manual or piece of documentation into another language, under the above
      conditions for modified versions, except that sections related to
      licensing, including this paragraph, may also be included in translations
      approved by the copyright holders of the respective licence documents in
      addition to the original English.

                                WARRANTY DISCLAIMER

      5. BECAUSE THIS MANUAL OR PIECE OF DOCUMENTATION IS LICENSED FREE OF CHARGE,
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