step_4

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Wed Nov  2 22:26:46 2016

@author: carissagadson
"""
## step 4 of challenge

import requests, json

## construct HTTP POST request
url4 = 'http://challenge.code2040.org/api/prefix'

headers1 = {'Content-Type': 'application/json'}

params1 = {'token': 'acfd4bea2a23e4735a50a5318245b87d'}

resp1 = requests.post(url4, data=json.dumps(params1), headers=headers1)

## turn resp1 from bytes to string
str_dict = str(resp1.content,'utf-8')
## turn string into useable dictionary
dict_of_str = json.loads(str_dict)
## initialize prefix as string to search for
prefix = dict_of_str["prefix"]
## initialize array as list of strings
array = dict_of_str["array"]

## get length of prefix
prefix_len = len(prefix)

## find all strings that start with prefix, and replace string with a 0 indicator
for index in range(len(array)):
    if array[index][:prefix_len] == prefix:
        array[index] = 0

## Note: At first I was using startswith() to find all strings starting with the prefix,
## but I found online that this method is maximized when the strings are quite long.
## Since the strings in this problem aren't very long, I decided to use this solution
## instead, thinking the runtime may be a bit faster. However, I'm not completely sure
## this is true.

## remove all elements with value 0 from list
array = list(filter(lambda x: x != 0, array))

## construct second HTTP POST request with solution
url4_1 = 'http://challenge.code2040.org/api/prefix/validate'

headers2 = {'Content-Type': 'application/json'}

params2 = {'token': 'acfd4bea2a23e4735a50a5318245b87d', 'array': array}

resp2 = requests.post(url4_1, data=json.dumps(params2), headers=headers2)

## print status
#print(resp2.status_code, resp2.reason)