solution.py

import requests
import pandas as pd
import matplotlib.pyplot as plt



def get_bls_key():
    """
    This method will get the BLS API key that is expected in api-key.txt file. That file is in the .gitignore and
    each user should have their own API key
    :rtype string
    """
    with open('api-key.txt', 'r') as api_key_file:
        api_key = api_key_file.read()
        return api_key

def get_request_data(series_id):
    r = requests.post(url=url, json={'seriesid': [series_id],
                                     'startyear': '2008',
                                     'endyear': '2017',
                                     'registrationkey': get_bls_key()}).json()
    return r['Results']['series'][0]['data']


# Task
coal_series = {'id': 'CEU1021210001',
               'name': 'Number of Coal Employees'}

gas_series = {'id': 'CEU1021100001',
              'name': 'Number of Gas Employees'}

url = 'https://api.bls.gov/publicAPI/v2/timeseries/data'

coal_data = get_request_data(coal_series['id'])
gas_data = get_request_data(gas_series['id'])

gas_data_frame = pd.DataFrame(gas_data)[::-1]

df = pd.DataFrame(coal_data)
df = df[::-1]
df['date_info'] = pd.to_datetime(df['year'] + ' ' + df['periodName'], format="%Y %B")
df['Number of Coal Employees'] = pd.to_numeric(df['value'])
df['Number of Gas Employees'] = pd.to_numeric(gas_data_frame['value'])

dates = df['date_info']
df.plot(x='date_info', subplots=True)
plt.ylabel("Number of Employees (in thousands)")
plt.show()