<< Chapter < Page Chapter >> Page >

Many different combinations of N, S, E, and W can be used to control the placement of the widget in the cell. A good explanation is provided in Layout within the Cell at TkDocs. The combination used in the second statement of Listing 2 causes the Frame to be stretched in all four directions so as to be stuck to all four sides of the root . In other words, the Frame completely fills the available space within the root container.

The last two statements in Listing 2 were explained by According to TkDocs above.

StringVar

To make a long story short, the StringVar objects shown in Listing 3 are used to connect the string values for feet and meters to the textvariable arguments of an Entry widget and a Label widget, which you will see later.

(If you connect a widget to a StringVar object using a textvariable argument, a change in the contents of either will cause a corresponding change in the other. This isdiscussed in some detail at 25.1.6.4. Coupling Widget Variables .)

Listing 3 . StringVar objects.
feet = StringVar() meters = StringVar()

The Entry widget

In the initial design stages of the GUI, the author indicates that the widgets will be placed in three columns and three rows.

The first statement in Listing 4 creates a new widget of the class Entry and saves the object's reference in the variable named feet_entry . According to The Tkinter Entry Widget ,

"The Entry widget is a standard Tkinter widget used to enter or display a single line of text."

The first argument is the parent -- in this case mainframe . This is followed by many possible optional arguments, one of which is width .

Listing 4 . The Entry widget.
feet_entry = ttk.Entry(mainframe, width=7, textvariable=feet) feet_entry.grid(column=2, row=1, sticky=(W, E))

The width argument

The Tkinter Entry Widget describes the width argument as follows:

"Width of the entry field, in character units. Note that this controls the size on screen; it does not limit the number of characters that can be typed into the entry field. The default width is 20 character."

The first statement in Listing 4 sets the width to seven characters.

The textvariable argument

The Tkinter Entry Widget describes the textvariable argument as follows:

"Associates a Tkinter variable (usually a StringVar) to the contents of the entry field."

This argument is set equal to feet from Listing 3 . From this point forward, values entered into the data entry field shown in Figure 2 will be saved in the StringVar named feet . This makes the value available to the calculate function that will be discussed later.

Make the Entry field visible

The author of the program explains that the first statement in Listing 4 creates the Entry widget but does not make it visible in the GUI. In order to make it visible, you must tell Tk where to place it relative to other widgets. Thisis accomplished by the call to grid in the second statement in Listing 4 , which places the Entry widget in column 2 and row 1. (Note that the author seems to have skipped column 0 and row 0 as described earlier .)

The sticky parameter in Listing 4 instructs Tk to stretch the Entry widget horizontally and make it touch both sides of the cell. (Note that manually stretching the size of the root on the screendoes not stretch the size of the Frame or the widgets contained in the Frame.)

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Itse 1359 introduction to scripting languages: python. OpenStax CNX. Jan 22, 2016 Download for free at https://legacy.cnx.org/content/col11713/1.32
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Itse 1359 introduction to scripting languages: python' conversation and receive update notifications?

Ask