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LESSON 11 OF 188 · BACKEND: HOW THE WEB WORKS

Follow the Pages in Python

Practice

A long list is rarely sent in one answer. APIs split it into pages: each answer holds a few items and says which page comes next. You keep asking until there is no next page.

You don't know in advance how many pages there are, so use a while loop that stops when the next page is None (JSON's null becomes None in Python). Here is the same idea on a plain dictionary, following a chain of bus stops:

next_stop = {"Home": "Park", "Park": "School", "School": None}
stop = "Home"
while stop is not None:
    print(stop)
    stop = next_stop[stop]

The supplier's /catalog has 5 products, 2 per page:

GET /catalog?page=1  →  {"page": 1, "items": ["Mug", "Notebook"], "next_page": 2}
GET /catalog?page=2  →  {"page": 2, "items": ["Lamp", "Pen"], "next_page": 3}
GET /catalog?page=3  →  {"page": 3, "items": ["Plant"], "next_page": null}

Your script must print:

Page 1
Mug
Notebook
Page 2
Lamp
Pen
Page 3
Plant

Your task: start at page 1 and keep asking /catalog for the page that next_page names, until it is None. For each page, print Page and its number, then every product name on it.


Assignment
Follow the Coding Tutorial to read every page of the catalog and print all its products.


Hint
Send the page number with params={"page": page}. Set page to data["next_page"] as the last line of the loop, or the script will ask for page 1 forever.


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    Web Pagination in Python

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