diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..744b7a9
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+icalendar
diff --git a/tools/gen_upcoming.py b/tools/gen_upcoming.py
index d611668..ff05fe7 100755
--- a/tools/gen_upcoming.py
+++ b/tools/gen_upcoming.py
@@ -1,22 +1,24 @@
 #!/usr/bin/env python3
 
 import sys
-from datetime import datetime, timedelta
-from dateutil.parser import parse
-from dateutil.rrule import rruleset, rrulestr
-import icalendar
-import locale
 import logging
-
+import locale
 from pprint import pprint
+from dateutil.parser import parse
+from datetime import datetime, timedelta
+from dateutil.rrule import rruleset, rrulestr
+
+import icalendar
+
 
 def vevent_to_event(event, rrstart=None):
 	if rrstart == None:
 		begin = parse(event['DTSTART'].to_ical())
 	else:
-		begin = rrstart 
+		begin = rrstart
 	return { "name": event['SUMMARY'].to_ical(), "url": event['URL'].to_ical(), "begin": begin }
 
+
 def parse_single_event(event, start, end):
 	logging.info("Processing single event %s" % event['SUMMARY'].to_ical().decode('utf-8'))
 	dtstart = parse(event['DTSTART'].to_ical())
@@ -25,6 +27,7 @@ def parse_single_event(event, start, end):
 	else:
 		return None
 
+
 def parse_recurring_event(event, start, end):
 	logging.info("Processing recurring event %s" % event['SUMMARY'].to_ical().decode('utf-8'))
 	dtstart = parse(event['DTSTART'].to_ical())
@@ -71,7 +74,8 @@ def format_events(events):
 			% (dateStr, event['url'].decode('utf-8'), event['name'].decode('utf-8')))
 	print('</table>')
 
-def main():
+
+if __name__ == "__main__":
 	if len(sys.argv) < 3:
 		print("Usage: %s calendar max_days max_items" % sys.argv[0])
 		sys.exit(-1)
@@ -84,5 +88,3 @@ def main():
 	events=find_events(calendar, datetime.now(), datetime.now() + timedelta(days=max_days), max_items)
 	format_events(events)
 
-if __name__ == "__main__":
-	main()
diff --git a/tools/merge_cals.py b/tools/merge_cals.py
index 463cd80..0df4949 100755
--- a/tools/merge_cals.py
+++ b/tools/merge_cals.py
@@ -1,25 +1,27 @@
 #!/usr/bin/env python3
 
 from glob import glob
-import icalendar
+
 import pytz
+import icalendar
 
-cals=[]
-merged=icalendar.Calendar()
+
+cals = []
+merged = icalendar.Calendar()
 merged.add('prodid', '-//CCCB Calendar Generator//berlin.ccc.de//')
-merged.add('version', '2.0') 
+merged.add('version', '2.0')
 
-for icsfilestr in glob("public/*/**/*.ics", recursive=True):
+for icsfilestr in glob('public/*/**/*.ics', recursive=True):
 	with open(icsfilestr, 'r') as icsfile:
-		print("Importing", icsfilestr)
+		print('Importing', icsfilestr)
 		cals.append(icalendar.Calendar.from_ical(icsfile.read()))
 
 for cal in cals:
 	for e in cal.subcomponents:
 		merged.add_component(e)
 
-outfile="static/all.ics"
+outfile = 'static/all.ics'
 with open(outfile, 'wb') as f:
-	print(f"writing to {outfile}...")
+	print(f'writing to {outfile}...')
 	f.write(merged.to_ical())
-	
+