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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 is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
How can I make nanorobot?
Lily
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
how can I make nanorobot?
Lily
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
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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
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