Phase 1 · Day 10 · Learn AI

Import styles

A module is a Python file (or package) you can import. Three common styles:

import math — then math.sqrt(9)
from math import sqrt — then sqrt(9)
import math as m — a short alias

Ways to import

import math
print(math.pi)
print(math.sqrt(16))

from random import choice, randint
print(choice(["train", "val", "test"]))
print(randint(1, 6))

import json as js
print(js.dumps({"ok": True}))

Avoid from module import * — it clutters your namespace and hides where names come from.

Standard library favorites

Before installing a package, check whether the stdlib already solves it. These show up constantly:

math, random, statistics, json, datetime, pathlib (locally), collections, itertools, re.

math, statistics, datetime

import math
import statistics
from datetime import datetime

values = [2, 4, 4, 4, 5, 5, 7, 9]
print(statistics.mean(values))
print(statistics.median(values))
print(math.ceil(2.1), math.floor(2.9))
print(datetime.now().strftime("%Y-%m-%d %H:%M"))

json encode/decode

import json

user = {"name": "Ada", "skills": ["python", "git"]}
text = json.dumps(user, indent=2)
print(text)

data = json.loads(text)
print(data["skills"][0])

json is how most APIs and config files talk—get comfortable with dumps (to text) and loads (from text).

Your own modules (local projects)

On your machine, helpers.py next to main.py can be imported with import helpers if you run from that folder.

Use if __name__ == "__main__": so a file can be both imported and run as a script.

Pattern for dual-purpose files

# imagine this is greeter.py
def greet(name):
    return f"Hello, {name}!"

if __name__ == "__main__":
    print(greet("Ada"))

# another file could: from greeter import greet

In the browser Try It panel you stay in one file—practice stdlib imports there, and create multi-file modules in VS Code.

Packages vs modules (preview)

A package is a folder of modules (often with __init__.py). pip installs third-party packages into your venv.

You already used venv on Day 7—tomorrow’s debugging day still uses only stdlib; project days may add small libraries later.

Typical project layout

my_app/
  main.py
  utils/
    __init__.py
    text.py
  requirements.txt
  .venv/

Practice

Mini challenge: experiment logger

Build a small script that creates a dict with experiment name (input), a random seed (randint), mean of [0.8, 0.82, 0.79], and a timestamp string. Print it as indented JSON.

challenge starter

import json
import statistics
from random import randint
from datetime import datetime

name = input("Experiment name: ")

record = {
    # TODO: name, seed, mean_score, created_at
}

print(json.dumps(record, indent=2))

Interactive

Try It in the browser

Use math.sqrt and statistics.mean on nums = [4, 9, 16, 25]. Print the square root of the mean, rounded to 2 decimals.

Output

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Errors

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Modules, Imports & Standard Library