Magic numbers in source (0.16 in three files) drift. Put settings in JSON (or similar) and load them once.

Goal

Write config.json, load it, and price a line with the file’s tax.

Write and load

import json
from pathlib import Path

Path("config.json").write_text(
    '{"city": "Nairobi", "tax": 0.16, "currency": "KES"}\n',
    encoding="utf-8",
)

cfg = json.loads(Path("config.json").read_text(encoding="utf-8"))
print(cfg["city"], cfg["tax"], cfg["currency"])

Use the config

import json
from pathlib import Path

Path("config.json").write_text(
    '{"city": "Kisumu", "tax": 0.16}\n',
    encoding="utf-8",
)
cfg = json.loads(Path("config.json").read_text(encoding="utf-8"))

def line_total(units, price, tax):
    return round(units * price * (1 + tax), 2)

print(cfg["city"], line_total(2, 10, cfg["tax"]))

Banner file

Download config.json, Add files, then:

import json
from pathlib import Path

cfg = json.loads(Path("config.json").read_text(encoding="utf-8"))
print(sorted(cfg.keys()))
print(cfg["city"])

Pitfall

Do not eval a config file. json.loads is enough for this course. YAML and TOML are extra libraries this tab may not have.