123 lines
5.4 KiB
Python
123 lines
5.4 KiB
Python
from datetime import datetime
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import urllib.request
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import xml.etree.ElementTree as ET
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today = datetime.now().strftime("%Y-%m-%d")
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""" this method calls a rss/XML Resource
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of Currency's and parses it to our
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needed exchange rate values.
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The return is a dictionary carring
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Key:Value pairs of new currencys.
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"""
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def get_exchange_rate():
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# During weekends there are no updates.
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# To develop i need a testresource.
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# In that case i comment the Online Resource block and uncomment the
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# development Block...
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# ~~~~~~~~~~~~~~~~~~~~~
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# Online Resource block:
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# ~~~~~~~~~~~~~~~~~~~~~
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SNB_URL = 'https://www.snb.ch/selector/de/mmr/exfeed/rss'
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urlsocket = urllib.request.urlopen(SNB_URL)
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root = ET.parse(urlsocket)
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root = ET.ElementTree(root)
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# ~~~~~~~~~~~~~~~~~~~~~
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# development block:
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# ~~~~~~~~~~~~~~~~~~~~~
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# root = ET.ElementTree(file='rss')
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# ~~~~~~~~~~~~~~~~~~~~~
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# Namespaces
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ns = {'rdf': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
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'none': 'http://purl.org/rss/1.0/',
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'dc': 'http://purl.org/dc/elements/1.1/',
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'dcterms': 'http://purl.org/dc/terms/',
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'cb': 'http://www.cbwiki.net/wiki/index.php/Specification_1.2/'
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}
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# Pathvariables to XML Namespaces
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none_path = 'none:item/'
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rate_path = 'cb:statistics/cb:exchangeRate/'
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observation_path = 'cb:statistics/cb:exchangeRate/cb:observation/'
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# THE FILE DATE:
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xml_datetime_string = root.find('none:channel/dcterms:created', ns).text
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# because of few knowlede just trim end of string to avoid error
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xml_datestring = xml_datetime_string.split('T')[0]
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# parse string to date object:
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xml_date = datetime.date(datetime.strptime(xml_datestring, "%Y-%m-%d"))
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exchange_rates = {}
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for item in root.findall('none:item', ns):
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# THE CURRENCY DATE:
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datetime_str = item.find('dc:date', ns).text
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# convert string to date object:
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# https://stackoverflow.com/a/12282040/4061870
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# seams like snb striked the microsecond somewhere between Nov. and
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# Dez. 2017 so maybe first check time type. "%Y-%m-%dT%H:%M:%S.%f%z"
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date = datetime.strptime(''.join(datetime_str.rsplit(':', 1)),
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"%Y-%m-%dT%H:%M:%S%z").strftime("%Y-%m-%d")
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# only the values of today are used so check for date:
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if date == today:
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title = item.find('none:title', ns).text
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base_currency = item.find(rate_path +
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'cb:baseCurrency', ns).text
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target_currency = item.find(rate_path +
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'cb:targetCurrency', ns).text
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CHFvalue = float(item.find(observation_path +
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'cb:value', ns).text)
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CHFvalue = float(CHFvalue) # convert to float
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FOREIGNvalue = CHFvalue # copy to new value to have both.
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unit = item.find(observation_path + 'cb:unit', ns).text
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decimals = int(item.find(observation_path +
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'cb:decimals', ns).text)
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# because it's dangerous to check for present, i check for none
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# here and have to do something in there so i set the target to 0.
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if item.find(observation_path + 'cb:unit_mult', ns) is None:
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unit_mult = float("1.0")
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else:
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# shift left by 2 digits with "/"
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# https://stackoverflow.com/questions/8362792/
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# because some currencys differ widly from CHF
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unit_mult = item.find(observation_path +
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'cb:unit_mult', ns).text
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# unit_mult defaults to '0' so we check for 8 decimal
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# values (2..-6) they represent the fracton value to
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# calculate the correct decimalpoint.
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if unit_mult == '2': # thinking of Bitcoins
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unit_mult = '0.01'
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if unit_mult == '1':
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unit_mult = '0.10'
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if unit_mult == '-1':
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unit_mult = '10'
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if unit_mult == '-2': # Japan Yen
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unit_mult = '100'
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if unit_mult == '-3':
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unit_mult = '1000'
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if unit_mult == '-4':
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unit_mult = '10000'
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if unit_mult == '-5':
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unit_mult = '100000'
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if unit_mult == '-6': # indian rupies
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unit_mult = '1000000'
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unit_mult = float(unit_mult) # convert to float
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# calculate the Currency to CHF:
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FOREIGNvalue = 1 / CHFvalue
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FOREIGNvalue *= unit_mult
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CHFvalue = CHFvalue / unit_mult
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# truncate it to decimal values provided by the xml:
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FOREIGNvalue_round = round(FOREIGNvalue, 5)
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# Print nice setup of all calculated currencys for Dev:
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# print("date:", date, " 1 ", target_currency, " costs: ",
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# CHFvalue, "CHF and 1 ", base_currency, " costs: ",
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# FOREIGNvalue_round, target_currency)
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exchange_rates.update(
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{target_currency: FOREIGNvalue_round})
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# Print the Dictionary:
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# print(exchange_rates)
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else:
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break
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return(exchange_rates, date)
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# for development its preferable to see that the for loop is done:
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# print('no more fresh data!')
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