python讀寫dbf文件
讀取遍歷dBASE或Xbase文件中的記錄。從Python的序列創建DBF文件。
import struct, datetime, decimal, itertoolsdef dbfreader(f): """Returns an iterator over records in a Xbase DBF file.
The first row returned contains the field names. The second row contains field specs: (type, size, decimal places). Subsequent rows contain the data records. If a record is marked as deleted, it is skipped. File should be opened for binary reads. """ # See DBF format spec at: # http://www.pgts.com.au/download/public/xbase.htm#DBF_STRUCT numrec, lenheader = struct.unpack('<xxxxLH22x', f.read(32)) numfields = (lenheader - 33) // 32 fields = [] for fieldno in xrange(numfields): name, typ, size, deci = struct.unpack('<11sc4xBB14x', f.read(32)) name = name.replace('\0', '') # eliminate NULs from string fields.append((name, typ, size, deci)) yield [field[0] for field in fields] yield [tuple(field[1:]) for field in fields] terminator = f.read(1) assert terminator == '\r' fields.insert(0, ('DeletionFlag', 'C', 1, 0)) fmt = ''.join(['%ds' % fieldinfo[2] for fieldinfo in fields]) fmtsiz = struct.calcsize(fmt) for i in xrange(numrec): record = struct.unpack(fmt, f.read(fmtsiz)) if record[0] != ' ': continue # deleted record result = [] for (name, typ, size, deci), value in itertools.izip(fields, record): if name == 'DeletionFlag': continue if typ == "N": value = value.replace('\0', '').lstrip() if value == '': value = 0 elif deci: value = decimal.Decimal(value) else: value = int(value) elif typ == 'D': y, m, d = int(value[:4]), int(value[4:6]), int(value[6:8]) value = datetime.date(y, m, d) elif typ == 'L': value = (value in 'YyTt' and 'T') or (value in 'NnFf' and 'F') or '?' elif typ == 'F': value = float(value) result.append(value) yield resultdef dbfwriter(f, fieldnames, fieldspecs, records): """ Return a string suitable for writing directly to a binary dbf file.
File f should be open for writing in a binary mode. Fieldnames should be no longer than ten characters and not include \x00. Fieldspecs are in the form (type, size, deci) where type is one of: C for ascii character data M for ascii character memo data (real memo fields not supported) D for datetime objects N for ints or decimal objects L for logical values 'T', 'F', or '?' size is the field width deci is the number of decimal places in the provided decimal object Records can be an iterable over the records (sequences of field values). """ # header info ver = 3 now = datetime.datetime.now() yr, mon, day = now.year-1900, now.month, now.day numrec = len(records) numfields = len(fieldspecs) lenheader = numfields * 32 + 33 lenrecord = sum(field[1] for field in fieldspecs) + 1 hdr = struct.pack('<BBBBLHH20x', ver, yr, mon, day, numrec, lenheader, lenrecord) f.write(hdr) # field specs for name, (typ, size, deci) in itertools.izip(fieldnames, fieldspecs): name = name.ljust(11, '\x00') fld = struct.pack('<11sc4xBB14x', name, typ, size, deci) f.write(fld) # terminator f.write('\r') # records for record in records: f.write(' ') # deletion flag for (typ, size, deci), value in itertools.izip(fieldspecs, record): if typ == "N": value = str(value).rjust(size, ' ') elif typ == 'D': value = value.strftime('%Y%m%d') elif typ == 'L': value = str(value)[0].upper() else: value = str(value)[:size].ljust(size, ' ') assert len(value) == size f.write(value) # End of file f.write('\x1A')-------------------------------------------------------
Example calls
if name == 'main': import sys, csv from cStringIO import StringIO from operator import itemgetter
# Read a database filename = '/pydev/databases/orders.dbf' if len(sys.argv) == 2: filename = sys.argv[1] f = open(filename, 'rb') db = list(dbfreader(f)) f.close() for record in db: print record fieldnames, fieldspecs, records = db[0], db[1], db[2:] # Alter the database del records[4] records.sort(key=itemgetter(4)) # Remove a field del fieldnames[0] del fieldspecs[0] records = [rec[1:] for rec in records] # Create a new DBF f = StringIO() dbfwriter(f, fieldnames, fieldspecs, records) # Read the data back from the new DBF print '-' * 20 f.seek(0) for line in dbfreader(f): print line f.close() # Convert to CSV print '.' * 20 f = StringIO() csv.writer(f).writerow(fieldnames) csv.writer(f).writerows(records) print f.getvalue() f.close()Example Output
""" ['ORDER_ID', 'CUSTMR_ID', 'EMPLOY_ID', 'ORDER_DATE', 'ORDER_AMT'] [('C', 10, 0), ('C', 11, 0), ('C', 11, 0), ('D', 8, 0), ('N', 12, 2)] ['10005 ', 'WALNG ', '555 ', datetime.date(1995, 5, 22), Decimal("173.40")] ['10004 ', 'BMARK ', '777 ', datetime.date(1995, 5, 18), Decimal("3194.20")] ['10029 ', 'SAWYH ', '777 ', datetime.date(1995, 6, 29), Decimal("97.30")] ['10013 ', 'RITEB ', '777 ', datetime.date(1995, 6, 2), Decimal("560.40")] ['10024 ', 'RATTC ', '444 ', datetime.date(1995, 6, 21), Decimal("2223.50")] ['10018 ', 'RATTC ', '444 ', datetime.date(1995, 6, 12), Decimal("1076.05")] ['10025 ', 'RATTC ', '444 ', datetime.date(1995, 6, 23), Decimal("185.80")] ['10038 ', 'OLDWO ', '111 ', datetime.date(1995, 7, 14), Decimal("863.96")] ['10002 ', 'MTIME ', '333 ', datetime.date(1995, 5, 16), Decimal("731.80")] ['10007 ', 'MORNS ', '444 ', datetime.date(1995, 5, 24), Decimal("1405.00")] ['10026 ', 'MORNS ', '555 ', datetime.date(1995, 6, 26), Decimal("17.40")] ['10030 ', 'LILLO ', '111 ', datetime.date(1995, 7, 3), Decimal("909.91")] ['10022 ', 'LAPLA ', '111 ', datetime.date(1995, 6, 19), Decimal("671.50")] ['10035 ', 'HIGHG ', '111 ', datetime.date(1995, 7, 11), Decimal("1984.83")]
['10033 ', 'FOODG ', '333 ', datetime.date(1995, 7, 6), Decimal("3401.32")]
['CUSTMR_ID', 'EMPLOY_ID', 'ORDER_DATE', 'ORDER_AMT'] [('C', 11, 0), ('C', 11, 0), ('D', 8, 0), ('N', 12, 2)] ['MORNS ', '555 ', datetime.date(1995, 6, 26), Decimal("17.40")] ['SAWYH ', '777 ', datetime.date(1995, 6, 29), Decimal("97.30")] ['WALNG ', '555 ', datetime.date(1995, 5, 22), Decimal("173.40")] ['RATTC ', '444 ', datetime.date(1995, 6, 23), Decimal("185.80")] ['RITEB ', '777 ', datetime.date(1995, 6, 2), Decimal("560.40")] ['LAPLA ', '111 ', datetime.date(1995, 6, 19), Decimal("671.50")] ['MTIME ', '333 ', datetime.date(1995, 5, 16), Decimal("731.80")] ['OLDWO ', '111 ', datetime.date(1995, 7, 14), Decimal("863.96")] ['LILLO ', '111 ', datetime.date(1995, 7, 3), Decimal("909.91")] ['RATTC ', '444 ', datetime.date(1995, 6, 12), Decimal("1076.05")] ['MORNS ', '444 ', datetime.date(1995, 5, 24), Decimal("1405.00")] ['HIGHG ', '111 ', datetime.date(1995, 7, 11), Decimal("1984.83")] ['BMARK ', '777 ', datetime.date(1995, 5, 18), Decimal("3194.20")] ['FOODG ', '333 ', datetime.date(1995, 7, 6), Decimal("3401.32")] .................... CUSTMR_ID,EMPLOY_ID,ORDER_DATE,ORDER_AMT MORNS ,555 ,1995-06-26,17.40 SAWYH ,777 ,1995-06-29,97.30 WALNG ,555 ,1995-05-22,173.40 RATTC ,444 ,1995-06-23,185.80 RITEB ,777 ,1995-06-02,560.40 LAPLA ,111 ,1995-06-19,671.50 MTIME ,333 ,1995-05-16,731.80 OLDWO ,111 ,1995-07-14,863.96 LILLO ,111 ,1995-07-03,909.91 RATTC ,444 ,1995-06-12,1076.05 MORNS ,444 ,1995-05-24,1405.00 HIGHG ,111 ,1995-07-11,1984.83 BMARK ,777 ,1995-05-18,3194.20 FOODG ,333 ,1995-07-06,3401.32 """</pre>