Dual conditions in D and Python

[Dennis Ritchie via Digitalmars-d-learn]

Hi,
In Python I can write this:

if (4 <= 5 <= 6):
    print ("OK")
-----
http://rextester.com/NNAM70713
In D, I can only write this:

import std.stdio;

void main() {

    if (4 <= 5 && 5 <= 6)
        puts("OK");
}
-----
http://rextester.com/FICP83173

I wanted to ask what is the reason? Maybe the program on Python's 
slower because of this? Or legacy C/C++ affected D?