slice_large_csv_file_small_files.py

rows = []
with open('large.csv', 'rb') as f:
    csvrows = csv.DictReader(f)
    for line in csvrows:
        rows.append(line)
chunks = [rows[x:x+45000] for x in xrange(0, len(rows), 45000) ]

for i, chunk in enumerate(chunks):
    print 'Chunk: {}/{}'.format(i, len(chunks))
    with open(str(i)+'.csv', 'wb') as f:
        dictwriter = csv.DictWriter(f, fieldnames=chunk[0].keys())
        dictwriter.writeheader()
        for c in chunk:
            dictwriter.writerow(c)