Immutable variables in python

apple9927

Why are there immutable variable types? ? Isn't this troublesome?

Such as:
num = 1
num = num + 2

In the above simple sentence, an int object is generated twice. Isn't this slower using python? ?

Is it slower to modify the value of a variable than to generate a variable? ?

Generating a variable is not more of a tool to do. Don't understand

Mandirigma

A variable is a bunch of addresses in the RAM, changing the value is changing the value of whatever is stored in the bunch of addresses. Generating a variable is saving RAM storage for that variable, then your code can put information in those storage spaces in RAM.

深蓝旅者

In C++, there is this situation
int a = 1;
a = a++ + ++a;
Variables are immutable or can avoid ambiguity

apple9927

Are there any other benefits? It is too much for this sacrifice. :)

thiefgroup

>> In the simple sentence above, two int objects were generated. Isn't this slower with python? ?
It’s not obvious whether you’re slow or not, just try it and you’ll know.

>> Could it be slower to modify the value of a variable than to generate a variable? ?

Immutable objects have many benefits, the most obvious is object sharing:

str1 = "abc"
str2 = "abc"
str3 = "abc"

Because "abc" is immutable, now only one "abc" object is needed.

If "abc" is variable, when str1 is modified, str2 and str3 must have a copy of "abc" independent of str1 in order not to be affected, so three objects are required.

And some applications require immutable data, such as dictionary keys. If you have learned hashing, you should be able to understand.

apple9927

People who come from C/C++, I want to learn python well, it is important to have two steps:

Immutable variables.

There are no character variables.

Not right, right? ?

thiefgroup

>> Immutable variables.
I don’t think it’s difficult to understand that immutable classes are often written in C++.

>> There is no character variable.
It's really a bit uncomfortable.

apple9927

I have always used C, and have never used C++ (although I have studied, I have only learned, I have not used it.)


There is no such thing as an immutable variable in C. It's a little awkward for me.

thiefgroup

Similar to const.

apple9927

I now use const to understand it.