The Secret Compiler Inside Python

https://www.youtube.com/watch?v=ujlk-CYEpJA Python is an interpreted language. You've heard it a thousand times. You write code, Python reads it line by line, runs it. No compilation. No binary. Just text in, results out. Except that's not what happens. Not even close. import dis def add ( a , b ): return a + b dis . dis ( add ) LOAD_FAST a LOAD_FAST b BINARY_OP ADD RETURN_VALUE That's bytecode . Compiled bytecode. Python's compiler turned your function into low-level instructions before it ever ran a single line. And those __pycache__ directories you've been ignoring? They're full of .pyc files — compiled bytecode cached on disk so Python doesn't recompile next time. Python has a compiler. It always has. The Hidden Pipeline When you run python script.py , your source code goes through three compilation stages — all hidden, all automatic: Tokenizer — rips your code apart. Every keyword, variable, and operator becomes a labeled token. def , name:add , open_paren ... Parser — assembles t