Retrieve postcodes for a list of longitudes and latitudes

fetch.py

import csv
import json

import requests
import pandas as pd
from pandas.io.json import json_normalize

url = "https://api.postcodes.io/postcodes"
api_limit = 99


def _construct_csv(result):
    output_csv = []
    for row in result["result"]:
        print(row)
        output = {}
        output["longitude"] = row["query"]["longitude"]
        output["latitude"] = row["query"]["latitude"]
        if (row["result"]):
            output["postcode"] = row["result"][0]["postcode"]
            output["region"] = row["result"][0]["region"]
            output["parish"] = row["result"][0]["parish"]
        output_csv.append(output)
    return output_csv


def _construct_json(input_csv):
    geocodes = []
    # Limit to 100, as this is the max for postcodes.io
    for _, row in input_csv.iterrows():
        g = {}
        g["longitude"] = row['long']
        g["latitude"] = row['lat']
        geocodes.append(g)

    request_json = {}
    request_json["geolocations"] = geocodes
    return request_json


def _api_request(request_json):
    response = requests.post(url, json=request_json)
    result = json.loads(response.content)
    return result


df = pd.read_csv("geocodes.csv", header=None, names=['id', 'long', 'lat'])
df.dropna(inplace=True)

total_rows = df.shape[0]
iterations = total_rows/api_limit

result_list = []
for i in range(0, round(iterations)):
    start = i * api_limit
    stop = start + api_limit
    df_slice = df.iloc[start:stop]

    request_json = _construct_json(df_slice)
    result = _api_request(request_json)

    result_list = result_list + _construct_csv(result)

output_df = json_normalize(result_list)
output_df.to_csv("output.csv", index=None, quoting=csv.QUOTE_NONNUMERIC)