noydb wrote:
> Paul Rubin wrote:
The Decimal module is pretty slow but is conceptually probably the right
way to do this. With just 50k records it shouldn't be too bad. With
more records you might look for a faster way.
from decimal import Decimal as D
from collections import defaultdict
records = ['3.14159','2.71828','3.142857']
td = defaultdict(int)
for x in records:
td[D(x).quantize(D('0.01'))] += 1
print td
I played with this - it worked. Using Python 2.6 so counter no good.
I require an output text file of sorted "key value" so I added
(further code to write out to an actual textfile, not important here)
for z in sorted(set(td)):
print z, td[z]
So it seems the idea is to add all the records in the particular field
of interest into a list (record). How does one do this in pure
Python?
Normally in my work with gis/arcgis sw, I would do a search cursor on
the DBF file and add each value in the particular field into a list
(to populate records above). Something like:
--> import arcgisscripting
--> # Create the geoprocessor object
--> gp = arcgisscripting.create()
--> records_list = []
--> cur = gp.SearchCursor(dbfTable)
--> row = cur.Next()
--> while row:
--> value = row.particular_field
--> records_list.append(value)
Are you trying to get away from arcgisscripting? There is a pure python
dbf package on PyPI (I know, I put it there ;) that you can use to
access the .dbf file in question (assuming it's a dBase III, IV, or
FoxPro format).
http://pypi.python.org/pypi/dbf/0.88.16 if you're interested.
Using it, the code above could be:
-----------------------------------------------------
import dbf
from collections import defaultdict
from decimal import Decimal
table = dbf.Table('path/to/table/table_name')
freq = defaultdict(int)
for record in table:
value = Decimal(record['field_of_interest'])
key = value.quantize(Decimal('0.01'))
freq[key] += 1
for z in sorted(freq):
print z, freq[z]
-----------------------------------------------------
Numeric/Float field types are returned as python floats*, so there may
be slight discrepancies between the stored value and the returned value.
Hope this helps.
~Ethan~
*Unless created with zero decimal places, in which case they are
returned as python integers.
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