We've written a requests-like library for web interfacing named Adafruit_CircuitPython_Requests. This library allows you to send HTTP/1.1 requests without "crafting" them and provides helpful methods for parsing the response from the server.
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
import board
import busio
from digitalio import DigitalInOut
from adafruit_wiznet5k.adafruit_wiznet5k import WIZNET5K
import adafruit_wiznet5k.adafruit_wiznet5k_socket as socket
import adafruit_requests as requests
cs = DigitalInOut(board.D10)
spi_bus = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
# Initialize ethernet interface with DHCP
eth = WIZNET5K(spi_bus, cs)
# Initialize a requests object with a socket and ethernet interface
requests.set_socket(socket, eth)
TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_GET_URL = "http://httpbin.org/get"
JSON_POST_URL = "http://httpbin.org/post"
attempts = 3 # Number of attempts to retry each request
failure_count = 0
response = None
print("Fetching text from %s" % TEXT_URL)
while not response:
try:
response = requests.get(TEXT_URL)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError(
"Failed to resolve hostname, \
please check your router's DNS configuration."
) from error
continue
print("-" * 40)
print("Text Response: ", response.text)
print("-" * 40)
response.close()
response = None
print("Fetching JSON data from %s" % JSON_GET_URL)
while not response:
try:
response = requests.get(JSON_GET_URL)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError(
"Failed to resolve hostname, \
please check your router's DNS configuration."
) from error
continue
print("-" * 40)
print("JSON Response: ", response.json())
print("-" * 40)
response.close()
response = None
data = "31F"
print("POSTing data to {0}: {1}".format(JSON_POST_URL, data))
while not response:
try:
response = requests.post(JSON_POST_URL, data=data)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError(
"Failed to resolve hostname, \
please check your router's DNS configuration."
) from error
continue
print("-" * 40)
json_resp = response.json()
# Parse out the 'data' key from json_resp dict.
print("Data received from server:", json_resp["data"])
print("-" * 40)
response.close()
response = None
json_data = {"Date": "July 25, 2019"}
print("POSTing data to {0}: {1}".format(JSON_POST_URL, json_data))
while not response:
try:
response = requests.post(JSON_POST_URL, json=json_data)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError(
"Failed to resolve hostname, \
please check your router's DNS configuration."
) from error
continue
print("-" * 40)
json_resp = response.json()
# Parse out the 'json' key from json_resp dict.
print("JSON Data received from server:", json_resp["json"])
print("-" * 40)
response.close()
The code first sets up the ethernet interface (eth). Then, it initializes a request object using a socket and the esp interface.
import board import busio from digitalio import DigitalInOut from adafruit_wiznet5k.adafruit_wiznet5k import WIZNET5K import adafruit_wiznet5k.adafruit_wiznet5k_socket as socket import adafruit_requests as requests cs = DigitalInOut(board.D10) spi_bus = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO) # Initialize ethernet interface with DHCP eth = WIZNET5K(spi_bus, cs) # Initialize a requests object with a socket and ethernet interface requests.set_socket(socket, eth)
HTTP GET with Requests
The code makes a HTTP GET request to Adafruit's WiFi testing website - http://wifitest.adafruit.com/testwifi/index.html.
To do this, we'll pass the URL into requests.get(). We're also going to save the response from the server into a variable named response. The call to requests.get() is wrapped in a loop which retries 3 times in the event of a failed request.
While we requested data from the server, we'd like to see what the server responded with. Since we already saved the server's response, we can read it back. Luckily for us, requests automatically decodes the server's response into human-readable text. You can read it back by calling response.text.
Lastly, we'll perform a bit of cleanup by calling response.close(). This closes, deletes, and collect's the response's data.
print("Fetching text from %s"%TEXT_URL)
while not response:
try:
response = requests.get(TEXT_URL)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError("Failed to resolve hostname, \
please check your router's DNS configuration.")
continue
print('-'*40)
print("Text Response: ", response.text)
print('-'*40)
response.close()
While some servers respond with text, some respond with json-formatted data consisting of attribute–value pairs.
CircuitPython_Requests can convert a JSON-formatted response from a server into a CPython dict object.
We can also fetch and parse json data. We'll send a HTTP get to a url we know returns a json-formatted response (instead of text data).
Then, the code calls response.json() to convert the response to a CPython dict.
print("Fetching JSON data from %s"%JSON_GET_URL)
while not response:
try:
response = requests.get(JSON_GET_URL)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError("Failed to resolve hostname, \
please check your router's DNS configuration.")
continue
print('-'*40)
print("JSON Response: ", response.json())
print('-'*40)
response.close()
HTTP POST with Requests
Requests can also POST data to a server by calling the requests.post method, passing it a data value.
data = '31F'
print("POSTing data to {0}: {1}".format(JSON_POST_URL, data))
while not response:
try:
response = requests.post(JSON_POST_URL, data=data)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError("Failed to resolve hostname, \
please check your router's DNS configuration.")
continue
print('-'*40)
json_resp = response.json()
# Parse out the 'data' key from json_resp dict.
print("Data received from server:", json_resp['data'])
print('-'*40)
response.close()
You can also post json-formatted data to a server by passing json_data into the requests.post method.
json_data = {"Date" : "July 25, 2019"}
print("POSTing data to {0}: {1}".format(JSON_POST_URL, json_data))
while not response:
try:
response = requests.post(JSON_POST_URL, json=json_data)
failure_count = 0
except AssertionError as error:
print("Request failed, retrying...\n", error)
failure_count += 1
if failure_count >= attempts:
raise AssertionError("Failed to resolve hostname, \
please check your router's DNS configuration.")
continue
print('-'*40)
json_resp = response.json()
# Parse out the 'json' key from json_resp dict.
print("JSON Data received from server:", json_resp['json'])
print('-'*40)
response.close()
