Popular recipes tagged "meta:min_python_3=*"

Uno (Text-Based) (Python)

2017-07-15T00:46:59-07:00

Python recipe 580811 by Brandon Martin (artificial_intelligence, cards, game, text_game, uno).

A text based recreation of the classic card game featuring functional AIs to play with. Some rules have been modified. User interface is text based, non-curses, using only simple python commands to draw it.

Frame with border color for Tkinter (Python)

2017-04-17T11:25:02-07:00

Python recipe 580735 by Miguel Martínez López (border, color, frame, tkinter).

This trick show how to add a border color to frame. These are the important configurations:

 highlightbackground="your border color here"
 highlightcolor="your border color here"
 highlightthickness="the border width"
 bd= 0

Tkinter table with scrollbars (Python)

2017-05-06T19:06:05-07:00

Python recipe 580793 by Miguel Martínez López (scrollbars, table, tkinter). Revision 13.

I created here a tkinter table with scrollbar support. I use one of my other recipes for the mousewheel support and scrolling:

https://code.activestate.com/recipes/580640-scrolling-frame-with-mouse-wheel-support

Equally-spaced numbers (linspace) (Python)

2015-01-12T22:16:37-08:00

Python recipe 579000 by Andrew Barnert (float, linspace, range, spread).

An equivalent of numpy.linspace, but as a pure-Python lazy sequence.

Like NumPy's linspace, but unlike the spread and frange recipes listed here, the num argument specifies the number of values, not the number of intervals, and the range is closed, not half-open.

Although this is primarily designed for floats, it will work for Fraction, Decimal, NumPy arrays (although this would be silly) and even datetime values.

This recipe can also serve as an example for creating lazy sequences.

See the discussion below for caveats.

Shoelace Formula for polygonal area (Python)

2017-07-17T05:53:45-07:00

Python recipe 580812 by Paddy McCarthy (2d, area).

Copied, by author from "Paddy3118 Go deh!: Python investigation of the Shoelace Formula for polygonal area http://paddy3118.blogspot.com/2017/07/python-investigation-of-shoelace.html#ixzz4n43Dqhaa " Where there is more meat on the bone (under a different license though).

PDF Text Extraction using fitz / MuPDF (PyMuPDF) (Python)

2016-03-17T12:00:06-07:00

Python recipe 580626 by Jorj X. McKie (cbz, epub, mupdf, openxps, pdf, pymupdf, text_extraction, xps).

Extract all the text of a PDF (or other supported container types) at very high speed. In general, text pieces of a PDF page are not arranged in natural reading order, but in the order they were entered during PDF creation. This script re-arranges text blocks according to their pixel coordinates to achieve a more readable output, i.e. top-down, left-right.

Simple multicolumn listbox for tkinter (Python)

2017-05-02T22:27:15-07:00

Python recipe 580794 by Miguel Martínez López (listbox, multicolumn, table, tkinter).

This recipe makes easy to work a treeview widget like a table.

It has several options for styling:

heading_anchor
heading_font
heading_background
heading_foreground
cell_anchor
cell_background
cell_foreground
cell_font
cell_pady
height
padding
adjust_heading_to_content
stripped_rows
headers
selection_background
selection_foreground
field_background

The "command" parameter is a callback and its called each time a row is selected.

groupby() For Unsorted Input (Python)

2017-05-12T10:40:58-07:00

Python recipe 580800 by Alfe (algorithm, datastructures, generators, grouping, lazy).

We all know the groupby() which is available in the itertools standard module. This one yields groups of consecutive elements in the input which are meant to be together in one group. For non-consecutive elements this will yield more than one group for the same key.

So effectively, groupby() only reformats a flat list into bunches of elements from that list without reordering anything. In practice this means that for input sorted by key this works perfect, but for unsorted input it might yield several groups for the same key (with groups for other keys in between). Typically needed, though, is a grouping with reordering if necessary.

I implemented a likewise lazy function (yielding generators) which also accepts ungrouped input.

Tkinter frame with gradient (Python)

2017-03-11T03:43:56-08:00

Python recipe 580761 by Miguel Martínez López (canvas, frame, gradient, tkinter). Revision 4.

Frame with linear gradient using PIL.

It's also possible to make the same trick using tkinter PhotoImage.

http://stackoverflow.com/questions/10417524/why-is-photoimage-put-slow

But PIL is more efficient:

https://groups.google.com/forum/#!topic/comp.lang.python/nQ6YO-dTz10

Possible values for orient are: VERTICAL, HORIZONTAL. If orient is "vertical", then width is mandatory. If orient is "horizontal", then height is mandatory. If steps is None, then the gradient is composed of adjacent lines.

One possible practical application of gradient frames are tool bars. Gradient guives a visual clue of when an area starts and when an area finish.

Tkinter search box (Python)

2017-04-08T12:27:36-07:00

Python recipe 580773 by Miguel Martínez López (entry, search, searchbox, tkinter). Revision 9.

Instead of using two colors for active background and normal background, I use only one color and opacity parameter.

I trigger the feeling of a button using different colors when the mouse is and isn't over. Many modern HTML search boxes uses the same approach.

Command function receives text of entry box when button is pressed.

Tkinter Link or Hyperlink Button (Python)

2017-04-07T11:51:26-07:00

Python recipe 580774 by Miguel Martínez López (button, hyperlink, link, tkinter, webbrowser). Revision 6.

If a background is not provided, the widget gets the background color from its container. The link button has two states: normal and visited. When the link is clicked, the state change to visited. When the link is clicked the action command is called. By default the text of the link has an underline. There is several options for customization.

I also added this megawidget to my "Metro UI Tkinter" recipe:

https://code.activestate.com/recipes/580729-metro-ui-tkinter

Variable Abbreviations (Python)

2017-06-22T11:57:20-07:00

Python recipe 580807 by Alfe (abbreviations, contextmanager, variables, with).

One sometimes has nice long speaking names vor variables, maybe things like buildingList[foundIndex].height, but would like to address these in a shorter fashion to be used within a formula or similar where lots of longs names tend to confuse any reader trying to understand the formula. Physicists use one-letter names for a reason.

For this I wrote a small context provider which allows using short names instead of long ones:

with Abbr(h=buildingList[foundIndex].height, g=gravitationalConstant):
    fallTime = sqrt(2 * h / g)
    endSpeed = sqrt(2 * h * g)
print("Fall time:", fallTime)
print("End speed:", endSpeed)

For longer formulas this can reduce ugly multi-line expressions to clearly readable one-liners.

One could use this:

h = buildingList[foundIndex].height
g = gravitationalConstant
fallTime = sqrt(2 * h / g)
endSpeed = sqrt(2 * h * g)
del g, h
print("Fall time:", fallTime)
print("End speed:", endSpeed)

to achieve the same result, but

it would not look as clean and
the context provider solves the typical issues like cleanup on exception etc.

Just using local variables without cleanup (like above without the del statement) also is an option of course, but that would clutter the variable name space unnecessarily.

CAVEATS: The implementation of Abbr() is a hack. If used as intended and described here, it should work just fine, though. But the hackish nature forces me to mention some things: Since at compile time the compiler decides that the h and g in the example must be global variables (because they aren't assigned in the function), it produces byte code accessing global variables. The context provider changes the global variable structure to fill the needs. (Overridden already existing global variables of the same name get restored properly at context exit.) This means some things:

One cannot have a local variable of the same name in the frame surrounding the context manager.
Existing global variables are changed during the time of the context manager; so using names like sys or os for abbreviations might be a bad idea due to side-effects.

Guard against an exception in the wrong place (Python)

2017-06-25T17:17:43-07:00

Python recipe 580808 by Steven D'Aprano (context, exception, guard, manager). Revision 2.

Sometimes exception handling can obscure bugs unless you guard against a particular exception occurring in a certain place. One example is that accidentally raising StopIteration inside a generator will halt the generator instead of displaying a traceback. That was solved by PEP 479, which automatically has such StopIteration exceptions change to RuntimeError. See the discussion below for further examples.

Here is a class which can be used as either a decorator or context manager for guarding against the given exceptions. It takes an exception (or a tuple of exceptions) as argument, and if the wrapped code raises that exception, it is re-raised as another exception type (by default RuntimeError).

For example:

try:
    with exception_guard(ZeroDivisionError):
        1/0  # raises ZeroDivisionError
except RuntimeError:
    print ('ZeroDivisionError replaced by RuntimeError')


@exception_guard(KeyError)
def demo():
    return {}['key']  # raises KeyError

try:
    demo()
except RuntimeError:
    print ('KeyError replaced by RuntimeError')

Unit Testing Nested Functions (Python)

2016-11-10T10:23:11-08:00

Python recipe 580716 by Alfe (introspection, nested, unittests). Revision 3.

Python allows the declaration of nested functions. These are typically hard to unit test because using just the normal ways of calling they cannot be called from outside their surrounding function. So they cannot be considered a clearly separated unit and thus cannot be unit tested.

This is a drawback of using them, so many developers (especially the ones deep into test driven development who strive to have a high unit test coverage) tend to avoid them in favor for standalone functions which can be called from the unit tests without any hassle.

But not all solutions with nested functions can be written as elegant with standalone functions. Nested functions are powerful insofar that they can access the local variables of the surrounding function without any need to pass them into the nested function, thus the code can in many cases stay neat and tidy while using a standalone function instead might raise the need to pass the complete context in form of a bunch of parameters. Also, using nested functions makes their local usage clear to any reader and keeps the name space tight.

But at least in the standard CPython (i. e. not necessarily in Jython, etc.) the implementation of functions (and methods) allows to find the nested function's code, wrap it properly to give it its needed context and then call it from the outside. I wrote a small module which helps doing exactly this.

Tkinter frame with different border sizes (Python)

2017-05-06T18:45:00-07:00

Python recipe 580798 by Miguel Martínez López (border, size, tkinter).

This trick shows how to create a bordered frame with different border size in each side.

Combobox Autocomplete (Python)

2017-04-03T15:17:26-07:00

Python recipe 580770 by Miguel Martínez López (autocomplete, combobox, entry, tkinter). Revision 11.

This is my own version of combobox autocomplete. The user can customize the matching function setting whether he wants to ignore case or whether the matching function should only match from the beginning of the string. The other possibility is to provide your own "auto complete function". The complete function returns all the found strings matching the text in the entry box.

It's also possible to customize the height of listbox and whether to use horizontal or vertical scrollbars.

Use arrows or Contro+n, Control+p to move selection on listbox.

This is a practical application of the combobox widget:

https://code.activestate.com/recipes/580771-tkinter-file-autocomplete-entry/

Tkinter entry with placeholder (Python)

2017-04-06T14:21:03-07:00

Python recipe 580768 by Miguel Martínez López (entry, placeholder, tkinter). Revision 8.

The function add_placeholder_to adds a placeholder to a tkinter entry.

Parameters:

entry: Tkinter widget to add placeholder
placeholder: Text of placeholder
color: Color of placeholder (optional)
font: Font of placeholder (optional)

A placeholder state object is attached to attribute "placeholder_state" of entry widget for future reference. It makes more easier to configure state of placeholder, or change the preferences of the user for color and font for the placeholder.

This widget is added also to my Metro Tkinter recipe:

https://code.activestate.com/recipes/580729-metro-ui-tkinter/

Tkinter Desktop Notifications or Popups (Python)

2017-04-01T19:27:59-07:00

Python recipe 580769 by Miguel Martínez López (alert, easing, notification, popup, tkinter). Revision 2.

This trick requires pytweening:

https://pypi.python.org/pypi/PyTweening

Install writing:

 pip install pytweening

It shows a notification on one corner of the screen,and gradually the notification disappears using an easing function. By default, it uses a linear easing function.

The class Notification_Manager has the method create_notification, but it also has some convenient methods to create easily some kind of notifications: success, alert, info, warning.

Tkinter Datepicker (like the jQuery UI datepicker) (Python)

2017-06-19T18:22:01-07:00

Python recipe 580725 by Miguel Martínez López (calendar, datepicker, megawidget, tkinter). Revision 18.

It's based on ttkcalendar.py. But the internals are totally changed.I don't use for example the Treeview widget. I added more features also:

On mouse over, the day label changes the background
The selected day has an outstanding style
Added support for many hotkeys

These are the default bindings:

Click button 1 on entry: Show calendar
Click button 1 outside entry and calendar: Hide calendar
Escape: Hide calendar
CTRL + PAGE UP: Move to the previous month.
CTRL + PAGE DOWN: Move to the next month.
CTRL + SHIFT + PAGE UP: Move to the previous year.
CTRL + SHIFT + PAGE DOWN: Move to the next year.
CTRL + LEFT: Move to the previous day.
CTRL + RIGHT: Move to the next day.
CTRL + UP: Move to the previous week.
CTRL + DOWN: Move to the next week.
CTRL + END: Close the datepicker and erase the date.
CTRL + HOME: Move to the current month.
CTRL + SPACE: Show date on calendar
CTRL + Return: Set current selection to entry

XML viewer for Tkinter or XML treeview (Python)

2017-02-22T23:00:21-08:00

Python recipe 580752 by Miguel Martínez López (browser, tkinter, treeview, viewer, xml). Revision 3.

Tk widget to display XML for Python. I use the treeview widget. There is no external dependency.I also added support for autoscrollbars.