Create Sequential Numeric ID in Groups

Question

I have a set of records:
OID,Type
1,A
2,B
3,A
4,B
5,C
6,C
7,B
8,B
9,A

I'd like to use a python script to add a sequential unique ID by type...
OID,Type,Type_Num
1,A,1
2,B,1
3,A,2
4,B,2
5,C,1
6,C,2
7,B,3
8,B,4
9,A,3

So far i've attempted looping through a list of types but with only partial success and i'm convinced i'm way off base as evidenced by code below...
rec=0
L=["A","B","C"]
def doit (Type) :
  for name in L :
    while Type == name :
      global rec
      rec = rec + 1
      return rec
    rec=0
__esri_field_calculator_splitter__
doit (!Type!)

My ultimate goal is to reference my records in the fashion A1, A2, A3, B1, B2, B3 etc.  Any thoughts or suggestions would be much appreciated.  Obviously i'm VERY new to Python.

ScottReaves · Answer

Thank you both, i believe this will get me there!

MathewCoyle · Answer

I have something like this.import arcpy
Acount = 0
Bcount = 0
Ccount = 0
rows = arcpy.UpdateCursor("mydata", "", "", "OID; Type; Type_Num", "OID A")

for row in rows:
    if row.Type == 'A':
        Acount = Acount+1
        row.Type_Num = Acount
    elif row.Type == 'B':
        Bcount = Bcount+1
        row.Type_Num = Bcount
    elif row.Type == 'C':
        Ccount = Ccount+1
        row.Type_Num = Ccount
    rows.updateRow(row)
del row
del rows

TerrySilveus · Answer

I have a set of records:
OID,Type
1,A
2,B
3,A
4,B
5,C
6,C
7,B
8,B
9,A

I'd like to use a python script to add a sequential unique ID by type...
OID,Type,Type_Num
1,A,1
2,B,1
3,A,2
4,B,2
5,C,1
6,C,2
7,B,3
8,B,4
9,A,3

So far i've attempted looping through a list of types but with only partial success and i'm convinced i'm way off base as evidenced by code below...
rec=0
L=["A","B","C"]
def doit (Type) :
  for name in L :
    while Type == name :
      global rec
      rec = rec + 1
      return rec
    rec=0
__esri_field_calculator_splitter__
doit (!Type!)

My ultimate goal is to reference my records in the fashion A1, A2, A3, B1, B2, B3 etc.  Any thoughts or suggestions would be much appreciated.  Obviously i'm VERY new to Python.

look at this link... a very similar question has been answered.
http://forums.arcgis.com/threads/27926-Find-Duplicates-and-increment