def sum_of_powers(end, power = 2, start = 1):
  return sum([(i) ** power for i in range(start, end + 1)])

sum_of_powers(10) # 385
sum_of_powers(10, 3) # 3025
sum_of_powers(10, 3, 5) # 2925

filename = "data.txt"
data = "Hello, World!"

with open(filename, "a") as file:
    file.write(data)

""" Currency Converter
----------------------------------------
"""
import urllib.request
import json
def currency_converter(currency_from, currency_to, currency_input):
    yql_base_url = "https://query.yahooapis.com/v1/public/yql"
    yql_query = 'select%20*%20from%20yahoo.finance.xchange%20where%20pair' \
                '%20in%20("'+currency_from+currency_to+'")'
    yql_query_url = yql_base_url + "?q=" + yql_query + "&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys"
    try:
        yql_response = urllib.request.urlopen(yql_query_url)
        try:
            json_string = str(yql_response.read())
            json_string = json_string[2:
            json_string = json_string[:-1]
            print(json_string)
            yql_json = json.loads(json_string)
            last_rate = yql_json['query']['results']['rate']['Rate']
            currency_output = currency_input * float(last_rate)
            return currency_output
        except (ValueError, KeyError, TypeError):
            print(yql_query_url)
            return "JSON format error"
    except IOError as e:
        print(str(e))
currency_input = 1
#currency codes : http://en.wikipedia.org/wiki/ISO_4217
currency_from = "USD"
currency_to = "TRY"
rate = currency_converter(currency_from, currency_to, currency_input)
print(rate)

# List
lst = [1, 2, 3, 'Alice', 'Alice']

# One-Liner
indices = [i for i in range(len(lst)) if lst[i]=='Alice']

# Result
print(indices)
# [3, 4]

from collections import defaultdict

def combine_values(*dicts):
  res = defaultdict(list)
  for d in dicts:
    for key in d:
      res[key].append(d[key])
  return dict(res)
  
d1 = {'a': 1, 'b': 'foo', 'c': 400}
d2 = {'a': 3, 'b': 200, 'd': 400}

combine_values(d1, d2) # {'a': [1, 3], 'b': ['foo', 200], 'c': [400], 'd': [400]}

def print_x_pattern(size):
    i,j = 0,size - 1

    while j >= 0 and i < size:

        initial_spaces = ' '*min(i,j)
        middle_spaces = ' '*(abs(i - j) - 1)
        final_spaces = ' '*(size - 1 - max(i,j))

        if j == i:
            print(initial_spaces + '*' + final_spaces)
        else:
            print(initial_spaces + '*' + middle_spaces + '*' + final_spaces)

        i += 1
        j -= 1

print_x_pattern(7)