Lesson 3 of 16 · 48 min · UG / professional
What actually runs: bytecode, CPython, frozen apps
You type a file. Something compiles it, something executes it. CPython is the usual engine on a college PC. Other engines and ‘frozen’ installers exist — you should know the names so a job ad does not sound like magic.
Application blueprint
A program is folders, config and a main door.
You will be able to
- ✓ Describe source → bytecode → execute
- ✓ Name CPython as the usual college engine
- ✓ Know frozen binaries and other implementations exist
Your file is not what the chip executes
The usual engine (CPython) reads your source, compiles it to bytecode (.pyc caches on a laptop), then a virtual machine runs that bytecode. You still debug the source. If the file is missing, nothing compiled — the launch failed first.
Other implementations exist (faster compilers, or Python on a JVM/CLR). Job ads name them. Until you have a reason, install the current CPython 3 from python.org or the campus image.
Frozen means ‘an installer, not a .py on the desktop’
Tools can bundle an interpreter plus your files into one executable so a clerk does not need Python on PATH. That is packaging, not a new language. Embedding means a C/C++ app starts Python internally — vendor kit territory.
You do not need to build a frozen app in this course. You do need to stop telling accounts ‘just install Python from a random blog’ when a frozen report would have been the handover.
Words that matter
- CPython
- The standard Python engine — what a college PC usually has.
- Bytecode
- The compiled form CPython actually steps through.
- Frozen binary
- An installer that already contains an interpreter + your code.
Common mistakes
Avoid: Emailing a .pyc and calling it the program.
Do this: Handover the .py (or a frozen build) plus a README that names the engine.
Run it step by step
Each box is a real program. Press Run, change a number, Run again — the output must follow your code.
1. Step 1 — source you can read
Humans ship this. The engine compiles it behind the scenes.
Edit the example, press Run, then Build if you want a compile check.
build
Press Build to compile.
2. Step 2 — a version stamp in config
Say which engine you tested. Tests can print it.
Edit the example, press Run, then Build if you want a compile check.
build
Press Build to compile.
Example program — Handover line
A clerk can read this. A compiler is not mentioned because they should not need one.
Edit the example, press Run, then Build if you want a compile check.
build
Press Build to compile.
Your turn — Stamp the engine
Print a line that includes both CPython and report.py.
Edit the example, press Run, then Build if you want a compile check.
build
Press Build to compile.
Self-assessment
Check your understanding before you mark the lesson complete.
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