Research: Make sure sqlAlchemy decimal places are rounded to two places

[jason-upchurch]

Summary

Querying the following in Chrome vs. Chrome Incognito mode yield results having different decimal places:

"https://api.open.fec.gov/v1/schedules/schedule_a/by_size/by_candidate/?sort_hide_null=false&page=1&api_key=DEMO_KEY&candidate_id=P80001571&election_full=false&per_page=20&cycle=2020&sort_null_only=false&sort_nulls_last=false"

Need to verify that decimal precision is set to maximum of 2 places in columns and operations. May need to consider rounding in final step for any operations having intermediate calculations to avoid accumulation of error.

Note that querying swagger ui and using the following script shows 2 decimal places:

import pandas as pd
import json
import requests

api_url = "https://api.open.fec.gov/v1/schedules/schedule_a/by_size/by_candidate/? 
    sort_hide_null=false&page=1&api_key=DEMO_KEY&candidate_id=P80001571&election_full=
    false&per_page=20&cycle=2020&sort_null_only=false&sort_nulls_last=false"

df = pd.read_json(api_url, typ=dict)
for r in df.results:
    print(r['total'])

response = requests.get(api_url)
print(json.loads(response.content.decode('utf-8')))

[edited formatting]

[jason-upchurch]

Closing issue as values are represented as expected in several environments. For the case of arithmetic on values representing dollars and cents, the case of results having greater than two decimal places can be explained as (see python documentation):

On most machines today, floats are approximated using a binary fraction with the numerator using the first 53 bits starting with the most significant bit and with the denominator as a power of two. In the case of 1/10, the binary fraction is 3602879701896397 / 2 ** 55 which is close to but not exactly equal to the true value of 1/10.

Many users are not aware of the approximation because of the way values are displayed. Python only prints a decimal approximation to the true decimal value of the binary approximation stored by the machine. On most machines, if Python were to print the true decimal value of the binary approximation stored for 0.1, it would have to display