How Do We Copy From One Register To Another In Lc3

In that location are many ways to copy a python list.

But first, let'due south talk about what copying a list actually means.

Let's take a look at this example

                >>> a = [i, two, 3, 4, 5] >>> b = a >>> a [1, 2, 3, 4, 5] >>> b [1, 2, iii, four, 5]              

In the example above, is b a copy of a?

The respond is actually No

b is in fact a, they both refer to the same python object.

Permit'south check what happens to b when nosotros modify a.

                >>> a[0] = 10 >>> b [10, 2, 3, four, 5]              

As you can see, irresolute the value of a[0] as well changes the value of b[0] because they both refer to the aforementioned list object.

And then what does copying a list mean?

Copying a python list means creating a new python object whose contents are identical.

The following figure shows what we desire to attain when we copy or clone a list.

In this commodity, we volition discuss three different methods to copy a python list.

The commencement two methods tin be used in python2 and python3 whereas the 3rd one works for python3 merely.

Showtime: Copying by Slicing

The almost common way (especially in python2) to copy a python list is to use slicing.

If yous accept been coding in python for a while, you probably came beyond some code that looks like this.

                >>> b = a[:]                              

When you omit the start alphabetize and the stop index from the slice, then your piece volition start from the start of the listing all the way to the end of the listing.

And because slicing creates a new object, and so the above code finer copies or clones the whole list into another list.

Allow's go ahead and confirm this.

                >>> a = [1, two, 3, seven] >>> b = a[:] >>> b [1, 2, three, 7] >>> id(a) 4440018888 >>> id(b) 4440454712              

This code confirms two things:

1- the items of listing b are the aforementioned as those of list a

2- a and b are different objects

Just how practise we know they are dissimilar?

I way is past observing that id(a) is different fromid(b).

If you don't know what the id() function does, information technology basically returns the address of a python object in the memory.

Needless to say, two variables will refer to the aforementioned object simply if the id of these two variable are exactly the same. Otherwise, they refer to different objects.

You want to be more assured?

Let's effort to modify a and meet if b remains unchanged.

If b is modified, then a and b refer to the same object.

If b remains unchanged, so a and b refer to two separate objects.

                >>> a = [1, ii, 3, 7] >>> b = a[:] >>> b [1, 2, 3, seven] >>> a[0] = -10 >>> a [-10, 2, iii, 7] >>> b [1, 2, three, 7]              

As you can see, after a was modified, b remains unchanged.

Awesome, we successfully copied a python list.

2d: Copying using listing() function

Some other way to create a copy of a list is to apply the list() congenital-in function.

The list() part is used to create a list object from whatever iterable.

And most of the time in real code, this iterable is not a list.

For example, the following code creates a newlist off of the items of a string.

                >>> southward = "how-do-you-do" >>> fifty = list(south) >>> l ['h', 'e', 'l', 'l', 'o']              

Merely since a list is an iterable itself, at that place is nothing that prevents y'all from creating a list from another list.

                >>> a = [1, 2, 3, 4] >>> b = listing(a) >>> b [1, ii, 3, 4] >>> id(a) 4354322312 >>> id(b) 4354377672              

Fifty-fifty though this is not a common way to copy a listing, it is even so a valid one.

Tertiary: Copying using the copy() Method

This is when Python3 comes to the rescue with a beautiful fashion to copy a list.

Python3 introduced a new method to lists chosen re-create() and it does exactly what you think information technology does.

It copies a list into another list.

                >>> a = [1, ii, 3, four] >>> b = a.copy() >>> id(a) 4354356936 >>> id(b) 4354322312              

The only downside is that it is not available in python2.

But if you are using python3, in that location is no fence this is the best, and near readable way to copy a list.

Decision

If you are using python2, you can copy a listing by slicing or by using the list() office.

If y'all are using python3, use the list'due south re-create() method.

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Source: https://www.afternerd.com/blog/python-copy-list/

Posted by: lloydbourre.blogspot.com

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