bcahue · September 24, 2014 15:04 · Sep 24, 2014
diff --git a/ConvertNewSteamID.markdown b/ConvertNewSteamID.markdown
@@ -0,0 +1,131 @@
+Seeing how SteamIDs have changed recently, I thought I'd write a Gist to help others (including myself!) decypher how to convert these from one format to the other in Python. First, let's go over basics to convert a 64bit CommunityID into a SteamID:
+
+```Python
+steamid64ident = 76561197960265728
+
+def commid_to_steamid(commid):
+  steamid = []
+  steamid.append('STEAM_0:')
+  steamidacct = int(commid) - steamid64ident
+
+  if steamidacct % 2 == 0:
+      steamid.append('0:')
+  else:
+      steamid.append('1:')
+
+  steamid.append(str(steamidacct // 2))
+
+  return ''.join(steamid)
+
+
+>>> commid_to_steamid(76561197994100486)
+'STEAM_0:0:16917379'
+```
+Remember that Python's // operator is for floor division, so the answer is always rounded down.
+
+And we can do the same in reverse, a SteamID turned into a CommunityID
+```Python
+def steamid_to_commid(steamid):
+  sid_split = steamid.split(':')
+  commid = int(sid_split[2]) * 2
+
+  if sid_split[1] == '1':
+      commid += 1
+
+  commid += steamid64ident
+  return commid
+
+
+>>> steamid_to_commid('STEAM_0:0:16917379')
+76561197994100486
+```
+The `if` statement that assigns the parity bit to the account number is a bit of a cheat here. Since the SteamID is a string, you don't have to use modulus to determine if you need to add the parity bit or not.
+
+Now onto the new SteamID3 format. The formula to convert old SteamIDs to the new SteamID3 format is this:
+`STEAM_X:Y:Z -> [U:1:(Z * 2 + Y)]`
+Be sure to note the brackets `[` and `]`, as they're considered part of the SteamID3 format.
+
+Here's how to convert a SteamID to SteamID3:
+```Python
+def steamid_to_usteamid(steamid):
+  steamid_split = steamid.split(':')
+  usteamid = []
+  usteamid.append('[U:1:')
+
+  y = int(steamid_split[1])
+  z = int(steamid_split[2])
+
+  steamacct = z * 2 + y
+
+  usteamid.append(str(steamacct) + ']')
+
+  return ''.join(usteamid)
+
+
+>>> steamid_to_usteamid('STEAM_0:0:16917379')
+'[U:1:33834758]'
+```
+We simply subtract the SteamID64Identifier from the CommunityID to get the SteamID3 account number. Here's the code:
+```Python
+def commid_to_usteamid(commid):
+    usteamid = []
+    usteamid.append('[U:1:')
+    steamidacct = int(commid) - steamid64ident
+
+    usteamid.append(str(steamidacct) + ']')
+
+    return ''.join(usteamid)
+
+
+>>> commid_to_usteamid(76561197994100486)
+'[U:1:33834758]'
+```
+Finally, I'll show how to convert the SteamID3 into CommunityIDs and SteamIDs. First, here's how to convert SteamID3 to a SteamID:
+```Python
+def usteamid_to_steamid(usteamid):
+  for ch in ['[', ']']:
+    if ch in usteamid:
+      usteamid = usteamid.replace(ch, '')
+
+  usteamid_split = usteamid.split(':')
+  steamid = []
+  steamid.append('STEAM_0:')
+
+  z = int(usteamid_split[2])
+
+  if z % 2 == 0:
+      steamid.append('0:')
+  else:
+      steamid.append('1:')
+
+  steamacct = z // 2
+
+  steamid.append(str(steamacct))
+
+  return ''.join(steamid)
+
+
+>>> usteamid_to_steamid('[U:1:33834758]')
+'STEAM_0:0:16917379'
+```
+The `for` loop is used to get rid of the brackets if they exist since they'll mess up our integer calculations. This could be simpified with [re](https://docs.python.org/3/library/re.html?highlight=re#module-re) but I wanted to do this without importing anything.
+
+Last but not least, here's how to convert a SteamID3 into a CommunityID:
+```Python
+def usteamid_to_commid(usteamid):
+  for ch in ['[', ']']:
+    if ch in usteamid:
+      usteamid = usteamid.replace(ch, '')
+
+  usteamid_split = usteamid.split(':')
+  commid = int(usteamid_split[2]) + steamid64ident
+
+  return commid
+
+
+>>> usteamid_to_commid('[U:1:33834758]')
+76561197994100486
+```
+Luckily this one is very easy, since USteamID account numbers already include the parity bit if required. All that's needed is to sanitize the input.
+
+Read more about SteamIDs [here](https://developer.valvesoftware.com/wiki/SteamID).
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