Pythonpytestpyproject.tomlAdvanced~10hPart 4 of 6

Python Craft

From a script to a project

Your code runs. It runs from one directory, on one machine, with one set of packages you cannot quite remember installing. This is the part where it becomes a thing you can hand over: installable, runnable from anywhere, checked by one command, and documented well enough that nobody has to ask you.

Start this projectSee the modules
Modules
7
Drills
13
Build steps
21
Time
~10h

Walk out with

A working script turned into an installed, tested, typed, configurable package another developer can clone and extend — behaviour unchanged.

What you'll do

01

Environments and imports

Which Python is running, and which file it actually loads.

02

The file that makes it real

Metadata, an editable install, a command you can run.

03

Checks and clear interfaces

One command that passes or fails, and honest types.

04

Onto somebody else's machine

Arguments, config, logging, and a README that works.

The pitch

What you practise, and what you leave with

A correct-but-unusable stock report script, rebuilt as an installed package with a CLI, config, logging, types, a quality gate and a README.

You will practise

  • Say which file an import actually loads
  • Read a version constraint
  • Say which value wins: default, env, or flag
  • Name whose job a complaint is

Afterwards you can

  • Explain why "works on my machine" happens
  • Lay out and install a real project
  • Make every check runnable with one command
  • Hand a codebase to somebody else

Modules

7 modules, 46 items

Lessons explain one idea. Drills repeat it until it sticks. Build steps make something that exists afterwards.

  1. 1

    Which Python is running?

    ~1h

    One import succeeds in one terminal and fails in another, with no file changed.

    • LessonThere is no such thing as "Python"14 min
    • Build stepBuild one and look inside it12 min
    • DrillWhich Python is that11 min
    • LessonSay what you need15 min
    • DrillRead a dependency line11 min
    • LessonHow much project is enough10 min
  2. 2

    Where the package lives

    ~1h

    A test that passes against the wrong copy, and the layout that prevents it.

    • LessonWhich copy wins15 min
    • DrillSay which file the import loads13 min
    • Build stepMove it to a src layout14 min
    • Build stepPoint the tests at the installed package13 min
    • DrillName the defect in the repository12 min
  3. 3

    The file that says what this is

    ~1h

    One file turns a folder into a project you can install and run.

    • LessonOne file, three jobs14 min
    • DrillWhich table states this10 min
    • Build stepFill the file in15 min
    • DrillSpot the broken line12 min
    • Build stepBuild it and look at what came out12 min
  4. 4

    Checks you can run again

    ~59 min

    Four tools with opinions, and one number that decides whether the gate passed.

    • LessonFour things that can object14 min
    • DrillWhose job is this complaint12 min
    • DrillRead the verdict10 min
    • Build stepMake it one command15 min
    • LessonWhat the gate is for8 min
  5. 5

    Say what goes in and out

    ~40 min

    A signature that is a guess, and the four annotations that make it a contract.

    • LessonA signature that is a guess14 min
    • DrillWhich signature says that11 min
    • Build stepRun the checker and fix the interface15 min
  6. 6

    Run it somewhere else

    ~2h

    Arguments in, configuration in, diagnostics out — and nothing you could not publish.

    • LessonThe contract on the command line14 min
    • DrillWhat the parser hands you12 min
    • Build stepGive it a real command line15 min
    • LessonConfiguration that travels9 min
    • DrillWhich value wins11 min
    • LessonCould you publish this tomorrow?9 min
    • DrillCould you publish this tomorrow10 min
    • LessonPrint, or log13 min
    • DrillHow much of this comes out11 min
    • Build stepWire configuration and logging16 min
  7. 7

    Turn it into a project

    ~3h

    Two hundred lines that work and cannot be handed over. Same behaviour, out the far side.

    • Build stepRead it, and write down what is wrong16 min
    • Build stepMake it a package22 min
    • Build stepGive it metadata and a way in18 min
    • Build stepTest the decision, not the printing11 min
    • Build stepChain them into one verdict11 min
    • Build stepAnnotate the public surface16 min
    • Build stepGive it a command line9 min
    • Build stepLet the machine configure it8 min
    • Build stepPut the diagnostics on a level9 min
    • Build stepWrite the documentation13 min
    • Build stepProve it on an empty machine12 min
    • Build stepAdd one thing nobody showed you20 min

The series

6 parts, in order

  1. 01Python Foundations~6h
  2. 02Python Fluency~5h
  3. 03Python Confidence~7h
  4. 04Python Craft~10h
  5. 05Python Design~8h
  6. 06Python Reach~7h

More in Languages

Keep going

All Languages projects
Part 1

Python Foundations

Read a program before you run it. Then write one worth showing.

Foundational~6h8 modules

Part 2

Python Fluency

Choose the shape before you type. Then say it in one line.

Intermediate~5h7 modules

Part 3

Python Confidence

Somebody else wrote it. Find out whether it works.

Advanced~7h7 modules

Part 5

Python Design

It works. It is also the wrong shape.

Advanced~8h7 modules

It works. Now make it somebody else's.

The first item is free. ~10h of focused work, at your own pace.

Start Python CraftAll projects

Advanced~10h7 modules