Internal working of Python

Python is an object-oriented high level programming language. Python is called an interpreted language. Python uses code modules that are interchangeable instead of a single long list of instructions that was standard for functional programming languages.

Python's simplicity and readability make it a popular and versatile language. However, its user-friendly facade masks a powerful engine that executes code efficiently. This article delves into Python's inner workings, unveiling the mechanisms that empower its capabilities

Python doesn't directly convert code to machine code. Instead, it uses the Python Virtual Machine (PVM) to execute bytecode, an intermediate representation that the PVM can understand. The most common implementation of Python, known as CPython, is the default and widely used version.

Internal working in Python

How Python Internally Works?

• Source code:

  This code is written by developers and contains the instructions for the program. Python source code files typically have the extension .py.

• Lexical Analysis (Scanning):

  The Python interpreter reads your code line by line and breaks it down into smaller meaningful units called tokens. These tokens include keywords (like if, def), identifiers (variable names like x), operators (+, -), literals (numbers, strings), and delimiters (parentheses, commas).

• Syntax Analysis (Parsing):

  • The tokens are then arranged into a grammatical structure called a parse tree. This tree represents the program's overall logic and how the tokens relate to each other. The parser checks if the code follows Python's syntax rules (e.g., proper indentation, correct use of keywords).

  • If any syntax errors are detected (e.g., missing parentheses or incorrect indentation), the interpreter raises an error.

• Abstract Syntax Tree (AST):

  • After successful parsing, the interpreter constructs an Abstract Syntax Tree (AST).

  • The AST represents the hierarchical structure of the program, capturing its semantics.

  • Each node in the tree corresponds to a syntactic construct (e.g., function call, loop, assignment).

• Bytecode Generation:

  • Python does not directly generate machine code like traditional compilers. Instead, it generates an intermediate code called bytecode.

  • The Python bytecode compiler translates the parse tree into bytecode, a lower-level intermediate representation that the Python virtual machine (PVM) can understand. Bytecode is a set of instructions optimized for the PVM.

  • This is like converting the sentence into a simplified code that a specific machine can interpret.

• Python Virtual Machine (PVM) Execution:

  • The PVM is a software layer that acts as a mediator between your Python code and the underlying computer hardware. It loads the bytecode instructions and executes them one by one. The PVM manages memory allocation, object creation, and interaction with system resources.

  • The PVM becomes the "interpreter" for the simplified code, carrying out the instructions on the actual computer.

  • In simple word the PVM is responsible for reading and executing Python code. It converts the human-readable Python code into bytecode, a low-level representation of the code that the PVM can understand and execute.

Interpreter vs. Compiler in Python

Python is an interpreted language, meaning the code is translated into bytecode first and then executed line by line by the Python interpreter. This allows for dynamic and interactive programming, but it can be slower compared to compiled languages like C++ or Java due to the interpretation process.

• Interpreter :

  An interpreter reads and executes the source code line by line, often without an intermediate step. This allows for dynamic and interactive programming but may incur a performance overhead. Languages like JavaScript and Python (partially) fall into this category.

• Compiler :

  A compiler translates the entire source code directly into machine code (or another low-level representation) specific to the target processor architecture. This machine code can be executed on the computer without further interpretation. Examples include C++ and Java compilers.

• In Summary:

  • Python's execution process involves elements of both compilation (bytecode generation) and interpretation (PVM execution).

  • This approach offers a balance between performance and flexibility.

  • Bytecode provides a portable intermediate representation that's platform-independent, while interpretation allows for dynamic changes and interactivity.

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