60 lines
2.2 KiB
Markdown
60 lines
2.2 KiB
Markdown
---
|
|
tags: [python]
|
|
---
|
|
|
|
# Python interpreter
|
|
|
|
## What is an implementation of a programming language?
|
|
|
|
An implementation of Python:
|
|
|
|
> means a program or environment which provides support for the execution of
|
|
> programs written in the Python language
|
|
|
|
As Python is interpreted, any implementation will perforce involve an
|
|
interpreting language.
|
|
|
|
There are three main implementations:
|
|
|
|
- CPython
|
|
- The default implementation, written in C
|
|
- Jython
|
|
- Python implemented by Java and running on the JVM
|
|
- PyPy
|
|
- A subset of Python which is faster due to machine code compilation
|
|
|
|
## CPython
|
|
|
|
In the standard implementation, the language which interprets Python code is C.
|
|
|
|
When Python runs in this implementation, code written in C converts it to
|
|
bytecode (so-called because each instruction is
|
|
[8-bits long](Binary_units_of_measurement.md)). This is a
|
|
lower-level transliteration of Python is not meant to be understood by the CPU
|
|
(since it is not binary) but rather to be run in the Python virtual machine
|
|
which is equipped to understand bytecode. The Python Virtual Machine is
|
|
therefore also known as "bytecode interpreter" or the CPython VM. The VM then
|
|
converts bytecode into machine-executable code.
|
|
|
|
The fact that Python does not compile to binary means that it can run on a
|
|
greater variety of hardwares however it is slower than a language that compiles
|
|
to machine code. PyPy is a solution for this because it is both interpreted and
|
|
compiled to optimised machine code at run time.
|
|
|
|
Where CPython is the interpreter, Python extensions can be written in C.
|
|
|
|
## PyPy
|
|
|
|
PyPy is an alternative implementation to CPython. The main difference is that it
|
|
uses a JIT-compiler and doesn't convert Python to the intermediary byte code. It
|
|
is also written in Python itself, specifically RPython ('restricted Python').
|
|
This is capable of converting Python directly to machine code without the
|
|
CPython virtual machine.
|
|
|
|
## Jython
|
|
|
|
Jython is an implementation of Python written in Java. Like CPython it converts
|
|
Python to bytecode but this runs on the JVM. As it is written in Java, a Jython
|
|
program can import and use any Java class.
|
|
|
|
Where Jython is the interpreter, Python extension can be written in Java.
|