Python is an interpreted language, which means that it needs an interpreter to execute its code. The Python interpreter reads source code written in Python, and converts it into an intermediate form called bytecode. This bytecode is then executed by the Python virtual machine (VM). The VM is responsible for managing memory, executing bytecode, and interacting with the operating system.
When Python source code is compiled, it is first parsed and then converted into an abstract syntax tree (AST). The AST is then compiled into bytecode using the built-in compile() function. The bytecode is a lower-level representation of the Python code that can be executed by the VM.
The bytecode is executed by the VM using a stack-based interpreter. Each bytecode instruction operates on the top few elements of the stack, and pushes or pops values as necessary. The bytecode interpreter is responsible for executing each instruction in the correct order and updating the stack accordingly.
Python also includes a number of optimization techniques that improve the performance of Python code. For example, Python includes a just-in-time (JIT) compiler that can dynamically compile frequently executed code into machine code, which can be executed much faster than bytecode. Additionally, Python includes a number of runtime optimizations, such as method inlining, that can further improve performance.
Overall, the internals of Python’s interpreter and virtual machine are complex, but understanding them can be helpful for optimizing Python code and developing custom tools or extensions for the language.