Put constants at top of script

sydney_tides.py

@@ -27,6 +27,7 @@ import math
 START_TIME = '2020-01-01'
 END_TIME = '2020-12-31'
 OUTPUT_NAME = 'levels.csv'
+MSL = 0.9952 
 
 harm = {}
 speed = 0
@@ -225,8 +226,6 @@ harm['NA2'] = [28.3986628, 0.0004, 16.9727]
 harm['MSO5'] = [72.9271398, 0.0001, 247.7639]
 harm['MSK5'] = [74.0251729, 0.0002, 189.3859]
 
-MSL = 0.9952
-
 # Now do the maths
 
 start_time = datetime.datetime.strptime(START_TIME, '%Y-%m-%d')