Elegant Python-Profiling the code hierarchy using the DIS module

Dis-disassembler for Python bytecode, that is, the Python code is disassembled into bytecode instructions.
Super easy to use: python-m Dis xxx.py

When I saw on the internet that while 1 was faster than while, I was confused and why was there such a difference?

Then use dis to go deep.

Suppose the est_while.py code is as follows.

#coding =utf-8while 1:    passwhile True:    Pass

The following is an analysis using DIS.

e:\>python-m dis test_while.py  2           0 setup_loop               3 (to 6)  3     >>    3 Jump_absolute            3  5     >>    6 setup_loop              (to)        >>    9 load_name                0 (True)             Pop_jump_ If_false       18

According to the official Python documentation, the DIS output report is in the following format.

The output is divided in the following columns:

1. The line number, for the first instruction
2. The current instruction, indicated as-->
3. A labelled instruction, indicated with >>
4. The address of the instruction,
5. The Operation code name,
6. Operation parameters, and
7. Interpretation of the parameters in parentheses.

The parameter interpretation recognizes local and global variable names, constant values, branch targets, and compare oper Ators.

As you can see, in the while 1 here (line 3rd), Direct is the jump_absolute instruction;

And while true here (line 5th) consists of load_name and pop_jump_if_false directives.

Original true in Python2 is not a keyword, just a built-in variable, bool type, the value is 1, that is, true+true output 2.
It can also be assigned value. For example, the assignment is true = 2 and can even be assigned a value of true = False.

So while true, each loop is checked for a value of true, corresponding to the instruction Load_name.

This is why while true is slower than while 1.

In Python3, however, true becomes the keyword. While 1 and while true have the same instructions, there is no performance difference.

Elegant Python-Profiling the code hierarchy using the DIS module