What is Python bytecode

Python is a hybrid interpreter. When running a program, it first assembles it into bytecode which can then be run in the Python interpreter (also called a Python virtual machine). The dis module in the standard library can be used to make the Python bytecode human-readable by disassembling classes, methods, functions, and code objects.

>>> def hello():
...     print "Hello, World"
...
>>> dis.dis(hello)
  2           0 LOAD_CONST               1 ('Hello, World')
              3 PRINT_ITEM
              4 PRINT_NEWLINE
              5 LOAD_CONST               0 (None)
              8 RETURN_VALUE

The Python interpreter is stack-based and uses a first-in last-out system.

Each operation code (opcode) in the Python assembly language (the bytecode) takes a fixed number of items from the stack and returns a fixed number of items to the stack. If there aren’t enough items on the stack for an opcode, the Python interpreter will crash, possibly without an error message.