This software was developed by Andrey Vasilchenko as a technical task for a job interview for a role of Digital Python Software Engineer at Direct Line Group (Ref:R-8128)

SOFTWARE ENGINEER PYTHON TEST

Create a REST endpoint that return the sum of a list of numbers e.g. [1,2,3] => 1+2+3 = 6 You are free to use any Python 3 framework, however, try and keep the usage of the third- party library to a minimum. The list of numbers is expected to arrive from a backend service and for this test you can hard code the list using the following line.

numbers_to_add = list(range(10000001))

The URL of the endpoint and the sample response is as follows: Request: http://localhost:5000/total Response:

{
"total": 6
}

Please provide the source code, tests, documentations and any assumptions you have made. Note: We are looking for the candidate’s “Software Engineering” ability not just the Python programming skills.

Assumptions

1. The input argument for the API coming from the backend should be in a JSON format {key/value} therefore I suggest using parameter n as the key value:

{n:[1,2,3]}

2. The amount of the input data should be limited to 100Mb or it might cause memory problems on the server. I suggest throwing an exception in case if the backend submit larger data

Installation

You can checkout and install the source from the github repository:

git clone https://github.com/directlinegroup/python_test.git
cd python_test
pip install -r requirements.txt

Execution

To run the server locally execute the following command in the folder where python_test was installed:

python3 src/api.py 

You should immediately see the confirmation that the server is up and running:

* Serving Flask app "api" (lazy loading)
 * Environment: production
 * Debug mode: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat

Tests

To run the unit tests open the folder python_test/tests in another terminal window and execute the following:

python3 -m unittest discover -v

You should get the following response

test_sum (test_api.TestDumps) ... ok
test_sum (test_api.TestFloat) ... ok
test_sum (test_api.TestJSON) ... ok
test_sum (test_api.TestMillion) ... ok
test_sum (test_api.TestParam) ... ok
test_sum (test_api.TestRandomMillion) ... ok
test_sum (test_api.TestString) ... ok
test_sum (test_api.TestSum) ... ok
test_sum (test_api.TestWrongParam) ... ok
test_sum (test_api.TestWrongParamDumps) ... ok

----------------------------------------------------------------------
Ran 10 tests in 38.092s

OK

Total API

The API supports the GET and POST methods and returns the total of the given numbers e.g. [1,2,3] => 1+2+3 = 6

To sum up the list of numbers, you should send them as array with n as a key e.g. {n:[1,2,3]} to the end point http://localhost:5000/total

The response you receive would be in the JSON format:

{
"total": 6
}

If you were constructing the URL by hand, this data would be given as key/value pairs in the URL after a question mark, e.g. http://localhost:5000/total?n=1&n=2&n=3

Or you can use any available third party frameworks to access the Total API but the following example is written in Python using Requests:

import requests   
 
url = 'http://localhost:5000/total'
numbers_to_add = {n:[1,2,3]}

response = requests.get(url, data= numbers_to_add)

print(response.text)

# {
# "total": 6
# }

You may want to send data that is not form-encoded. If you pass it in a string instead of a dict, that data will be posted directly. The Total API accepts JSON-Encoded POST/PATCH data:

import json

url = 'http://localhost:5000/total'
numbers_to_add = {n:[1,2,3]}

response = requests.get(url, data= json.dumps(numbers_to_add))

Exceptions

If you try to access the API without sending the list or not using the parameter n in the requests, you will receive the following error:

Argument "n" is not found

If you submit a large amount of data (over 100Mb), the Total API will raise another error:

Content is too big