Why are variables in Python different from other programming languages'? [closed]

Question

According to what I know, a variable in Python is a name that refers to a value stored in the computer memory, like a label on a box.

but in other programming languages a variable is a location, in memory, where values are stored, and it's like a box.

• Why does that difference exist?

• Python Documentation doesn't tell us what a variable is, so how do Python book authors know what it is?

Answer 1

This is not a Python vs Other Languages distinction - it's actually Value Types vs Reference Types distinction. Python uses reference types, and while many modern languages also tend to use reference types, it's common to compare Python(or any language, actually) to C/C++, which use value types.

(I'm simplifying things a lot here - there are languages that support both reference and value types, languages that use value types usually have pointers, which are the value-type version of reference types, and some languages that use reference types use value types for primitives)

With reference types - like what Python uses - the variable refers to the "box" in the memory. This means that multiple variables may refer to the same box:

class Foo:
    x = 1

foo = Foo()
bar = foo
bar.x = 10
print(foo.x)  # prints 10

When we changed bar.x, foo.x was changed as well. This is because foo and bar are both labels to the same box.

Compare with this C code:

#include<stdio.h>

struct Foo {
    int x;
};

int main(int ARGC, char** ARGV) {
    struct Foo foo, bar;
    foo.x = 0;
    bar = foo;
    bar.x = 10;
    printf("%d\n", foo.x); // prints 0
    return 0;
}

C uses value types, so foo and bar are not "labels" - they are the boxes themselves. That's why when we change bar.x, foo.x does not change - they are different boxes, and bar = foo does not make bar refer to the same box as foo like it did in Python - instead, it copies the content of the foo box into the bar box.