For Loops in Python Khan Academy English Serbian

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Now that we know a little bit about lists,

Sada kada znamo nešto o listama,

I thought I would use this video to introduce you

pomislio sam da iskoristim ovaj snimak

to loops, and in particular for loops.

da vas upoznam sa petljama, i to posebno sa <i>for</i> petljama

And if we have time, we might do other types of loops.

(i ako budemo imali vremena možemo da uradimo i druge vrste petlji).

But before we even do that, I want

Ali pre nego što to uradimo,

to introduce you to a built-in Python function called Ranger.

želim da vas upoznam sa ugrađenom funkcijom Python-a

When I say built-in, it means it comes with Python.

koja se naziva <i>range()</i> -- a kada kažem "ugrađena" to znači da ona dolazi u okviru Python-a.

And it's really a way to generate

I to je u stvari način da se naprave liste

lists that have integers that increment.

- liste koje imaju cele brojeve kao inkremente.

So for example, if I just say, range of 6,

Tako, na primer, ako samo kažem, interval od šest [<i>range(6)</i>]

it generates a list from 0 through 5.

program pravi listu od 0 do 5.

So it's 6 elements up to, but not including, 6.

Dakle to je 6 elemenata, ali ne uključujući broj 6.

If I wanted to include 6, I would have to do range of 7.

Ukoliko želim da uključim i broj šest, onda moram da napravim interval od sedam [<i>range(7)</i>].

And then I go all the way up to, but not including 7.

I onda bih dobio listu koja ide do, ali ne uključuje, broj 7,

But I get 6 in there.

ali uključuje 6.

If I want to have 1 through 6, if I

Ako želim da imam listu od 1 do 6

don't want to have that 0 there, I could do range starting at 1

- ne želeći da imam 0 u njoj - mogao bih da napravim interval koji počinje sa 1

and including 1, up to, but not including 7.

i uključuje 6, ali ne uključuje 7.

So the first item here will be included.

Dakle, prvi element ovde bi bio uključen,

The last item will not be included.

a zadnji element ne bi bio uključen u listu.

And there we go. We get 1, 2, 3, 4, 5, 6.

I onda dobijamo - eto ga, dobijamo 1 2 3 4 5 6

And what's cool about these integrated development

I ono što je super

environments, these IDE's, this pie scripter that I'm running,

u ovom integrisanom razvojnom okruženju (<i>IDE</i>), ovi IDE-ovi, ovaj PyScripter koji koristim,

is that, when I type in a function that it recognizes,

je to što kada unesem funkciju koju on prepoznaje,

it actually will tell me a little bit

on će mi zapravo reći

something about that function, in case you forget it.

ponešto o funkciji, u slučaju da zaboravim.

So I don't know if you can read this here,

Dakle, ja ne znam da li možete da pročitate ovo ovde, ali piše,

but it says, range, start, stop, step.

"<i>range([start,] stop, [step])</i>"

tako da možete takođe, ukoliko želite, da kažete, koliko da...

So right now, the default is to increment by 1 each time.

Znači upravo sad, predefinisano je da se radi inkrement od po 1 svaki put.

But it says, hey, I could tell you

to increment by a different number.

"Hej, mogu da ti kažem da povećaš za <b>drugu</b> vrednost!"

So let's say you have a range.

Na primer, recimo da imamo interval,

Say you start at 0, and you want to go up to 8.

i da počinjemo sa nulom i želimo da raste do 8.

And I want to go up by 2, instead of 1.

I da želimo da raste za 2 umesto za 1.

So then I went to 0, 2, 4, 6-- I should have said it more

Onda smo dobili [0, 1, 2, 4, 6] i ja

precisely-- up to, but not including 8.

... ja sam to trebao reći preciznije.

The upper part of the range, you don't include it.

Do 8, ali ne <b>uljučujući</b> 8 - na gornjem delu intervala, 8 nije ukljuceno.

So it goes up to that, and it increments it by 2.

Dakle, interval ide do 8 sa povećanjem od 2,

So you could do it like that.

tako da možete to uraditi na taj način

So maybe you want to start at 3, and you want to go up to, but not including-- I don't know. Let me do up to, but not including 31.

ili možda želite da počnete od 3 i da idete nagore do 31, ali da ne uključite 31

And you want to go up by steps of 3.

i želite da koristite skokove od 3, evo ga.

So there you go. It went up steps by 3, up to, but not including 31.

[?] do, ali ne uključujući 31.

So it can generate a whole bunch of lists.

Sada se može napraviti nekoliko listi

And the reason why this is useful is because we can use these inside of loops.

i razlog zbog kog je ovo korisno je to što možemo da koristimo interval unutar petlji.

And so the first type of loop I'm going to introduce you to

I sada prvi tip petlje

sa kojom ću vas upoznati je <i>for</i> petlja.

So this was the interpreter down here.

Ovo dole je interpreter,

Here, I'm going to actually write a program.

ovde ću zapravo da pišem program.

So this program is really just to show you a for loop does.

Koristiću ovaj program samo da vam pokažem

So I could say, for i-- and i is this variable that's often

za šta služi <i>for</i> petlja. Dakle, mogu da kazem "<i>for i</i>" i <i>i</i> je promenljiva

used in for loops, in iterative loops.

koja se koristi u <i>for</i> i drugim iterativnim petljama

And iterative means you keep doing something over and over

a iterativno znači

again-- for i in-- and let me just do a simple one-- in range-- and I'm just

da se ista operacija ponavlja ispočetka, iznova i iznova. "<i>for i in</i>", i dopustite mi da uradim jednostavnu funkciju, "<i>in range</i>",

going to say 5-- range of 5.

i samo ću da kažem, 5, "range(5)"

So this will generate a list, 0, 1, 2, 3, 4.

Ovo će napraviti listu, [0, 1, 2, 3, 4],

So for i in range 5.

dakle "<i>for i in range(5)</i>" i ova kolona kaže:

And this colon says, now we're going

"Sada ćemo da imamo poduslov

to have a sub clause of what to do on each of those iterations.

koji se odnosi na ono što treba da bude urađeno u svakoj od ovih iteracija."

Let's just print out what i is.

Hajde da ispišemo šta je <i>i</i>.

And so, before we even see what this is going to do,

I pre nego što vidimo šta će se dogoditi,

let's just think about it.

hajde da razmislimo o tome.

It's saying, for each time we go through this loop,

Kaže, "svaki put kada idemo kroz ovu petlju",

for each of the things in the range, make i refer to them.

"za svaku od ovih stavki u intervalu",

And then each of those loops is going to refer a different one.

"napravi da se <i>i</i> refrencira na njih", i onda će se svaka od tih petlji

And you want to print it out.

odnositi na različitu,

So let's just try this out.

"i onda ćeš da je prikažeš."

So let me save this program.

Hajde da isprobamo.

And now, let me run it.

Sačuvaću program, a sad hajde da ga pokrenem.

So there you go.

What it did is it created a loop.

Ono šta je program uradio jeste da je napravio petlju,

So each time it goes to the loop,

tako da svaki put kada ide kroz petlju

it assigns i to a different element in this list.

dodeljuje <i>i</i> različitom elementu u ovoj listi.

As you remember, this list was 0, 1, 2, 3 and 4.

Kao što se sećate, ova lista je bila [0, 1, 2, 3, 4]

Did I say 0, 1, 2, 3, 4, 5 before?

(Da li sam rekao 0,1,2,3,4,5 ranije?

No, it's 0, 1, 2, 3, 4, up to, but not including 5.

Ne, samo je 0,1,2,3,4 - do 5, ali ne uključujući 5.)

And so, each time you go through the loop,

Dakle, svaki put kada prođe kroz ovu petlju, on prolazi kroz svaku od ovih stavki

it goes through each of those items. And this program really just says, print out that i.

i ovaj program samo kaže "prikaži to <i>i</i>".

So the first time we go to the loop, i is 0.

Tako da prvi put kada prođe kroz petlju, <i>i = 0</i> tako da program štampa [0].

So it prints it out. Then it prints out 1.

Zatim štampa 1, a onda 2,

Then it prints a 2. Then it prints a 3.

zatim 3 i na kraju 4.

Then it prints a 4. So it just keeps going through it that many times.

Dakle, program samo prolazi kroz petlju toliko puta.

If we said this was for range 10.

Da smo rekli "<i>for range(10):</i>",

Now let's run this program, you'll

sad pokrenimo program.

see it'll print 1 through 9.

Pogledajmo, prikazaće...

brojeve od 1 do 9. Prikazaće od 1 do 9.

I should say 0 through 9, because that's

Ili, trebalo bi da kažem od 0 do 9!

the first element in this list.

Jer je to prvi element u ovoj listi.

But you could do more interesting things.

Ali možemo uraditi i neke interesantinije stvari.

Let's say that you wanted to take the sum of 0 through 9.

Recimo da želite da dobijte zbir brojeva od 0 do 9.

So what you could do is you could define another variable

U tom slučaju, možete da definišete drugu promenljivu ovde.

here, sum. So before I do anything, the sum is just going to be 0.

Dakle, pre nego što uradim bilo šta, zbir će biti 0.

And then what you could say is, each time you go

I ono što bih mogao da kažem je,

through the loop, why don't you define sum

"svaki put kada prođes kroz petlju, zašto ne bi..." "dodao zbiru, definisao ga kao prethodni zbir..."

to be the previous sum plus what i is in this part of the loop?

"plus ono što je <i>i</i> u ovom delu petlje."

And just so that we can keep track of it,

I da bismo pratili sve operacije,

I then want to print the sum.

ja ću tada prikazati sumu.

Now let's see what this thing does.

Pogledajmo šta ova stvar radi.

So let's try it out. So let me save it, and then let me run it.

Sačuvaću program i pokrenuti ga.

So there you go.

So the first time we went to the loop, sum is zero. Sum is 0 and i is 0.

Prvi put kada prođe kroz petlju, zbir je 0 i <i>i</i> je jednako 0, saberemo ih,

You add them together. You print the sum, you get 0.

prikažemo sumu, i dobijemo 0.

The next time we go through the loop, i is 1.

Sledeći put kada prođe kroz petlju,

We add that to the previous sum, which was 0, print it,

<i>i</i> je jednako 1. Dodajmo 1 prethodnoj sumi (0),

prikažemo je, i dobićemo 1.

Then the next time through the loop, i is now going to be 2.

Sledeći put kada prođe kroz petlju, <i>i</i> je jednako 2.

Add that to the previous sum, 2 plus 1, you get 3.

Dodajmo 2 prethodnoj sumi, 2 + 1, i dobićemo 3.

Next time through the loop, i is 3.

Sledeći put kada prođe kroz petlju,

You add that to the previous sum, you get 6.

<i>i</i> je jednako 3. Dodajmo 3 prethodnoj sumi i dobićemo 6.

So the sum of all the numbers, 0 through 9, is 45.

I tako, kad saberemo sve brojeve, od 0 do 9, zbir je 45.

So just that, that's actually a kind of a useful program.

Ovo je primer korisnog programa.

But just to make the point a little bit clearer,

Samo da iznesem ovo malo jasnije,

let me actually walk you through this on my little drawing

proći ćemo zajedno kroz sve ovo

tablet. So let me close my-- let me paste my code that I just

koristeći moju malu tablu za crtanje. Kopiraću svoj kod, koji sam upravo napisao ovde.

wrote up here. And let's just think about what this is doing.

I razmislimo šta ovo radi.

So we have a couple of variables here.

Dakle, imamo nekoliko promenljivih ovde.

We start off with this variable sum that is set to 0.

Počećemo sa ovom promenljivom "<i>sum</i>" čija je vrednost podešena na nulu.

And there's two ways to visualize variables.

Postoje dva načina da se prikažu promenljive.

A common way to visualize it-- and this

Uobičajen način da zamislite promenljive

isn't necessarily wrong, this is sometimes an easier way

(ne mora da bude pogrešno,

to think about it-- is to view them as buckets.

ponekad je lakše da se misli na ovaj način o problemu) je da se na njih gleda kao na kontejnere.

But in Python, the really correct way-- and you

Ali u Python-u, zaista ispravan način

saw why that's important with lists--

(i videli ste to sa listama)

is to view them as referring to something.

je da se o njima misli kao da pokazuju na nešto.

So if you view them as buckets, you can say, OK,

Dakle, ako ih posmatrate kao kontejnere, mozete reći

from the get go, the number in the sum bucket is 0.

OK, od samog početka,, broj u "<i>sum</i>" kontejneru je 0.

But the reality is, is that the variable sum is now

Ali stvarnost je da

referring to the numeric literal, the actual number 0, sitting in memory someplace.

promenljiva "<i>sum</i>" sada pokazuje na numeričku vrednost, na stvarni broj 0, koji čuči negde u memoriji.

Now we enter into the for loop.

Sada ulazimo u <i>for</i> petlju.

And what the for loop says is, let's iteratively assign i to each of the elements in the list generated

I ono što petlja radi jeste da iterativno dodeljuje <i>i</i> svakom od elemenata

by a range of 10.

u listi koju je kreirala komanda <i>range(10)</i>.

So just to be clear, if we called this right over here,

Da razjasnimo, ako pozovemo ovo, baš ovde, interval od 10,

range of 10, this will generate a list that looks like this. So it will generate a list 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, up

ovo će stvoriti listu koja izgleda ovako:

to, but not including 10.

sve do 10, ali ne uključujući 10,

This is 10 elements right over here.

ovih deset elemenata ovde.

And then we go into the for loop.

I sada ulazimo u <i>for</i> petlju.

So the first time we go through the for loop-- and let me write it-- so I'll think about it

Prvi put kad prolazimo kroz <i>for</i> petlju...

two different ways.

Razmisliću o tome na dva različita načina.

So one, I'll think about it in the bucket way.

Prvo ću misliti o tome na "kontejner" način.

So we have this variable, i, that can actually only

Imamo ovu promenljivu <i>i</i>,

be used inside of this clause.

koja se može koristiti samo unutar ovog uslova,

We'll talk more about scope or where a variable can be used.

(govorićemo više o opsegu,

But this i variable is only good inside of this clause.

ili gde promenljive mogu biti korišćene, ali ova promenljiva <i>i</i> je dobra samo unutar ovog uslova.

The sum variable, the way I've defined it,

<i>Sum</i> promenljiva, s obzirom na način na koji sam je definisao,

I can use it anywhere, outside of the clause, or inside of it,

mogu da je koristim bilo gde -

because it was defined outside of the clause.

izvan ili unutar ovog uslova, zato što je definisana van uslova.)

So you have your i.

Dakle, imamo <i>i</i>

So this is if you think of it as a bucket.

ako mislite o tome kao o kontejneru

And so, through the first iteration, i is assigned to this first item over here.

prva iteracija je dodeljena ovoj prvoj stavci ovde.

So i is going to be 0.

Tako da ce <i>i</i> biti jednako 0.

The better way to think about it is i

U stvarnosti, bolji način da se misli o ovome

is actually referring to this first element, our first time

jeste taj da <i>i</i> pokazuje na prvi element

through the loop.

tokom našeg prvog prolaza kroz petlju.

And then we go through the loop, and it says sum plus i.

I kada prođemo kroz petlju, a ona kaže "<i>sum + i</i>"

Well, sum is 0. And i is 0. You add them together, you get 0.

pa, <i>sum</i> je jednako 0 i <i>i</i> je 0, saberemo ih i dobijemo 0.

So sum is still going to be 0, or still referring to 0.

Dakle, <i>sum</i> će i dalje da bude 0, odnosno i dalje će pokazivati na 0.

And then it prints the sum out. So then this line right over here prints sum.

I kada prikažemo <i>sum</i>, ova linija ovde,

It says, OK, the sum right now is just-- let me do it in blue-- it's just 0.

kaže, "OK, <i>sum</i> je sada samo 0",

And it printed it out.

Then it goes back to the for loop

Zatim opet odlazi do <i>for</i> petlje i kaže:

and says, look, are there any more elements that I can assign i to?

"Pogledaj, ima li još elementata na koje mogu da ukažem promenljivom <i>i</i>?"

Well, sure there are.

Pa, sigurno da ima!

There's all of these that we have to go through.

Postoje svi ovi kroz koje tek treba da prođemo.

So then it makes i the next element in the sequence.

Tada, postavlja da <i>i</i> pokazuje na sledeći element u nizu,

So now i is going to be the next element in the sequence.

pa će sad <i>i</i> biti sledeći element

Or another way to think about it is in the i bucket--

u nizu, ili razmišljajući o tome na drugi način - nalazi se u "i" kontejneru,

if you want to view them as buckets--

ako hoćete da ih tretiramo kao kontejnere,

i is now set equal to 1.

<i>i</i> sada ima vrednost 1. I sad pokrenućemo ovo ponovo.

And now we run this again. And we say, OK, sum is 0 plus i.

I kazemo:"OK, <i>sum</i> je 0, plus <i>i</i>, <i>i</i> je 1.

I is 1. So sum is now going to refer to 1. Or another way to think about it is sum

Pa <i>sum</i> će sad da ukazuje na 1."

is now going to refer to 1.

And when you print sum, it'll now print 1.

I kada odštampamo <i>sum</i>, dobićemo 1.

Then, the for loop will say, alright,

Onda <i>for</i> petlja kaže,

are there any more elements in this list right over here

"Pogledaj, ima li još elementata

to assign i to?

na koje mogu da ukažem promenljivom <i>i</i>?"

Well, sure there are.

Pa, sigurno da ima!

There's all of these others, so let me keep going.

Postoje svi ovi kroz koje treba tek da prođemo, pa zato - nastavimo dalje!

So i can now be equal to, or can refer to, 2.

Sada, <i>i</i> može biti jednako (odnosno može da ukazuje na) 2.

So if you think of it as a bucket, i is now 2.

Ako posmatrate <i>i</i> kao kontejner, <i>i</i> je sada 2,

Or you could say, i is now referring to 2.

ili možete reći da <i>i</i> sada ukazuje na 2

And you could ignore these right over here.

(a možete i da to sada ignorišete).

And we go through the loop again.

I idemo ponovo kroz petlju, <i>sum</i> je sada 1,

Sum is now 1. 1 plus i, i is now 2. 1 plus 2 is 3.

<i>1 + i</i>, <i>i</i> je sada 2, <i>1 + 2</i> je 3.

So sum is now going to be 3 this time through the loop.

Dakle <i>sum</i> će da bude 3

So sum is now referring to 3. You print sum, you get 3.

prilikom ovog prolaska kroz petlju. Dakle, sada <i>sum</i> pokazuje na 3, prikazujemo <i>sum</i> i dobićemo 3.

And you keep going all the way.

I ako nastavimo da idemo ovim putem, <i>i</i> će nastaviti da pokazuje

As we go through the loop, the loop

sve dok idemo kroz petlju,

will still keep going, as there's

petlja će se nastavljati

more things that i can refer to.

sve dok ima još elemenata na koje <i>i</i> može da pokazuje,

We can keep incrementing i to these other values over here.

tako da možemo nastaviti sa povećavanjem <i>i</i> i na ove preostale vrednosti ovde.

And eventually, i is going to be 9.

I na kraju, i će biti 9,

We're going to evaluate this.

proverićemo ovo,

And the for loop says, hey, is there

i <i>for</i> petlja ce reći,

anything left in this list that i can be?

"Hej, postoji li još nešto u listi čiju vrednost <i>i</i> može dobiti?"

And you're like, no, there isn't anything left in this list.

I vaš odgovor je u fazonu: "Ne! Ništa više nije ostalo u ovoj listi!"

And then the loop is going to be done.

I onda će petlja biti gotova,

And we'll break out to it.

prekinuće se i program će stati.

And the program will stop. And that's exactly what we saw happening, when we ran the program over here.

I to je upravo ono što smo videli da se dešava kada smo ovde pokrenuli program.

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