Add Constants class in utilities

utilities.py

@@ -1,10 +1,46 @@
+from collections import namedtuple
 import hashlib
 from pandas import read_csv
 
+class _ReadOnlyProperty(object):
+    def __init__(self, value):
+        self.value = value
+    
+    def __get__(self, obj, objtype):
+        return self.value
+
+    def __Set__(self, obj, value):
+        return NotImplementedError("Cannot change a constant.")
+
+
+class Constants(object):
+    db_location = _ReadOnlyProperty('https://aresvalley.com/Storage/Artemis/Database/data.zip')
+    ref_loc = _ReadOnlyProperty('https://aresvalley.com/Storage/Artemis/Database/data.zip.log')
+    data_folder = _ReadOnlyProperty('Data')
+    spectra_folder = _ReadOnlyProperty('Spectra')
+    audio_folder = _ReadOnlyProperty('Audio')
+    icons_folder = _ReadOnlyProperty('icons_imgs')
+    __Band = namedtuple("Band", ["lower", "upper"])
+    __ELF = __Band(0, 30) # Formally it is (3, 30) Hz.
+    __SLF = __Band(30, 300)
+    __ULF = __Band(300, 3000)
+    __VLF = __Band(3000, 30000)
+    __LF  = __Band(30 * 10**3, 300 * 10**3)
+    __MF  = __Band(300 * 10 ** 3, 3000 * 10**3)
+    __HF  = __Band(3 * 10**6, 30 * 10**6)
+    __VHF = __Band(30 * 10**6, 300 * 10**6)
+    __UHF = __Band(300 * 10**6, 3000 * 10**6)
+    __SHF = __Band(3 * 10**9, 30 * 10**9)
+    __EHF = __Band(30 * 10**9, 300 * 10**9)
+    bands = _ReadOnlyProperty((__ELF, __SLF, __ULF, __VLF, __LF, __MF, __HF, __VHF, __UHF, __SHF, __EHF))
+    active_color = _ReadOnlyProperty("#39eaff")
+    inactive_color = _ReadOnlyProperty("#9f9f9f")
+    conversion_factors = _ReadOnlyProperty({"Hz":1, "kHz":1000, "MHz":1000000, "GHz":1000000000})
+
+
 def checksum_ok(data, what):
     code = hashlib.sha256()
     code.update(data)
-    ref_loc = 'https://aresvalley.com/Storage/Artemis/Database/data.zip.log'
     if what == "folder":
         n = 0
     elif what == "db":
@@ -12,7 +48,7 @@ def checksum_ok(data, what):
     else:
         raise ValueError("Wrong entry name.")
     try:
-        reference = read_csv(ref_loc, delimiter = '*').iat[-1, n]
+        reference = read_csv(Constants.ref_loc, delimiter = '*').iat[-1, n]
     except HTTPError:
         return False
     return code.hexdigest() == reference