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Using Python to interact with an API

Objectives

In this module, you will learn:

  • How to use the requests library to make HTTP requests
  • How to pass query parameters
  • How to read the response status and parse JSON

The requests library

Python's standard library can make HTTP requests, but it is a bit sluggish. The requests library is very user-friendly (and powerful!) and is widely used.

Installing

Install requests into your virtual environment: 

pip install requests

Forgetting something?

Update your requirements file with the new library!

Making a GET request

import requests

response = requests.get("https://www.fruityvice.com/api/fruit/banana")

There are two ways to construct a query with parameters:

  • Query parameters can be appended to the URL manually: 

    url = "https://www.fruityvice.com/api/fruit/fat?min=5"

  • Let requests build the URL for you by supplying a params parameter to the request. This is much easier to parse and looks cleaner. 

    response = requests.get(
    "https://www.fruityvice.com/api/fruit/fat",
    params={"min": 5},
)

print(response.url)     # confirm that requests built the right URL

requests will encode and append the parameters to the URL for you.

Working with the response

The response object contains everything the server sent back. See this w3schools article for documentation on the response object.

print(response.status_code)     # hopefully, 200

data = response.json()          # parses the JSON response into a Python object
print(data)                     # inspect the output
print(data["name"])
Always check the status code

It is a good idea to always check if a response was succesful. Below are some ways to do so:

assert 200 <= response.status_code < 300

response.raise_for_status()  # built-in method of requests.response, raises an exception if unsuccesful

If a request failed, the response body can still have valuable information on what went wrong.

Exercise

Repeat the Fruityvice exploration from the previous section, but this time entirely in Python. You can copy the code examples above to a new Python file, and modify it.

  • Look up your least favourite fruit by name and print its protein content.
  • Request all fruits and find the one with the highest sugar content.
  • Try requesting a fruit that does not exist. What status code do you get? Does the response contain any information?
Bonus points
  • Be neat and reproducible! Use functions for repeated code, naming conventions, documentation, etc.
  • Add the Python file you wrote to Git
    • More bonus: commit and push it to remote