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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.


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 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

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
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
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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