Running Python¶

Before writing programs, we must understand how Python code is executed.

Python code can be run in several ways:

1. Interactive Interpreter¶

The Python interpreter allows immediate evaluation of expressions.

Example session:

>>> 2 + 3
5
>>> "hello".upper()
'HELLO'

Each line entered into the interpreter is evaluated immediately.

2. Running a Script¶

Python programs are commonly stored in .py files.

Example file:

print("Hello, Python!")

Run it from the command line:

python hello.py

Output:

Hello, Python!

3. Program Execution Model¶

When Python runs a script, it performs the following steps:

flowchart TD
    A[Python source code] --> B[Interpreter]
    B --> C[Bytecode compilation]
    C --> D[Python Virtual Machine]
    D --> E[Program output]

The interpreter translates Python code into bytecode, which is executed by the Python Virtual Machine (PVM).