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