Python's CSV reader and iteration

Via generators. You can build all kinds of complexity from simple generator-filter functions. While considerably more complex than your filter, this is more extensible and can easily handle really complex spreadsheets.

def skip_blank( rdr ):
    for row in rdr:
        if len(row) == 0: continue
        if all(len(col)==0 for col in row): continue
        yield row

def after_heading( text, rdr ):
    i= iter(rdr)
    for row in i:
        if any( column == text for column in row ):
            break
    for row in i:
        yield row

def before_footing( text, rdr ):
    for row in rdr:
        if any( column == text for column in row ):
            break
        yield row

def between( start, end, rdr ):
    for row in before_footing( end, after_heading( start, rdr ) ):
        yield row

for row in between( 'Grand Total', 'Client Account', skip_blank( inputFile ) ):
    print row

you can do it like this, by setting flag

import csv
file = "file"
f=0
reader = csv.reader(open(file),delimiter=',')
for row in reader:
    if "Grand Total" in row: break
    if "Client Account" in row: f=1;continue
    if f:
        if row[0].isdigit():
            print row

import re
import StringIO

data=re.search("Client Account[^\r\n]+[\r\n]+(.*)(?=Grand Total)",open(filename).read(),re.DOTALL).group(1)
datafile=StringIO.StringIO(data)

inputFile = csv.reader(datafile, dialect='excel')
records = [line for line in inputFile if line and line[0].isdigit()]

Use a nice little generator for something like this. This one could be generalized a little more if your requirements change:

def lines_between(source, first, second):
    for line in source:
        if line and line[0] == first:
            break

    for line in source:
        if line: and line[0] == second:
            break

        if line:  # only non-empty lines
            yield line

for record in lines_between(inputFile, 'Client Account', 'Grand Total'):
    # process record

You didn't ask explicitly for the "non-empty lines" filter, but your own approach was doing this so I assume you wanted it. If you don't want to process the rows "lazily" like that, but just want a list with everything built in advance, do this:

records = list(lines_between(inputFile, 'Client Account', 'Grand Total'))

By the way, on Windows, be sure to open the real source file using binary mode, with csv.reader(open(filename, 'rb'), dialect='excel') as the csv docs note.