Can Python Requests library be used on Google App Engine?

Not yet but hopefully very soon. Support for GAE is being worked on – see issue #498 (App Engine Fixes).

Requests uses urllib3 which in turn uses httplib which is supported on GAE as a wrapper for urlfetch API. Although urllib3 uses some modules not available on GAE this usage is deliberately made optional so that urllib3 can be used on GAE.

No, in a more recent post, the developers say they do not support GAE because it’s too different from python.

Install the requests-toolbelt library:
https://github.com/sigmavirus24/requests-toolbelt

For App Engine it could be something like: pip install requests-toolbelt -t lib

(See: https://cloud.google.com/appengine/docs/python/tools/using-libraries-python-27#installing_a_library)

Then add:

from requests_toolbelt.adapters import appengine
appengine.monkeypatch()

In your main.py or equivalent.

Edit: this solution is now part of the official documentation: https://cloud.google.com/appengine/docs/python/issue-requests#issuing_an_http_request
(in the REQUESTS tab)

this is now possible, I got it working using this combination of workarounds in appengine_config.py:

# Step 1: first add requests and requests-toolbelt to your requirements.txt (or however you install them via pip)
# Step 2: in appengine_config.py add the following snippet:

# see https://cloud.google.com/appengine/docs/python/issue-requests#issuing_an_http_request
import requests
import requests_toolbelt.adapters.appengine

# Use the App Engine Requests adapter. This makes sure that Requests uses
# URLFetch.
requests_toolbelt.adapters.appengine.monkeypatch()

# also monkey patch platform.platform() from https://code.google.com/p/googleappengine/issues/detail?id=12982
import platform

def patch(module):
    def decorate(func):
        setattr(module, func.func_name, func)
        return func
    return decorate


@patch(platform)
def platform():
    return 'AppEngine'

Yes you can use the requests module.
GCP does not support the use of Requests library out of the box. So we will have to make some tweeks to make it work.
In order to deploy an application on the Google App Engine, we need to make a main.py(where main python flask app resides) and app.yaml(configuration file needed to run it in GCP).
Here is a sample code for the app.yaml file for python 2.7 environment

runtime: python27
api_version: 1
threadsafe: true

handlers:
- url: /.*
  redirect_http_response_code: 301
  script: main.app

libraries:
- name: flask
  version: 0.12

Now we need to configure the requests library to use URLfetch internally.
To use requests, we’ll need to install both requests and requests-toolbelt using the vendoring instructions. (https://cloud.google.com/appengine/docs/standard/python/tools/using-libraries-python-27#installing_a_library).
Basically we need to install our custom libraries.

1. Create a directory to store your third-party libraries, such as lib/
   mkdir lib
2. Upload the requests and requests-toolbelt libraries from your system or download them directly into the lib folder created in earlier step.
3. Use pip (version 6 or later) with the -t flag to copy the libraries into the folder you created in the previous step. For example:
   pip install -t lib/ (pip install -t lib/ requests)
4. Create a file named appengine_config.py in the same folder as your app.yaml file.

5. Edit the appengine_config.py file and provide your library directory to the vendor.add() method.
   Sample appengine_config.py file

   from google.appengine.ext import vendor
   # Add any libraries install in the "lib" folder.
   vendor.add('lib/requests')
   vendor.add('lib/requests_toolbelt')
   

6. Once installed, use the requests_toolbelt.adapters.appengine module to configure requests to use URLFetch.
   Copy the below code to the start of your main.py file

   import requests
   from requests_toolbelt.adapters import appengine
   appengine.monkeypatch(validate_certificate=True)
   

(https://cloud.google.com/appengine/docs/standard/python/issue-requests)

Now we can easily use the requests library to make get/post requests.
Test your app:

dev_appserver.py --port=<port number> app.yaml

To fix up requests to work with Google App Engine but also allow my application to run outside of GAE, I added the following code:

try:
    from google.appengine.api import urlfetch
    from requests_toolbelt.adapters import appengine
    appengine.monkeypatch()
except ImportError:
    pass