python读写dbf文件，,读取遍历dBASE或Xb

读取遍历dBASE或Xbase文件中的记录。从Python的序列创建DBF文件。```pythonimport struct, datetime, decimal, itertools

def 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_STRUCTnumrec, lenheader = struct.unpack('<xxxxLH22x', f.read(32))    numfields = (lenheader - 33) // 32fields = []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 result

def 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 objectRecords can be an iterable over the records (sequences of field values)."""# header infover = 3now = datetime.datetime.now()yr, mon, day = now.year-1900, now.month, now.daynumrec = len(records)numfields = len(fieldspecs)lenheader = numfields * 32 + 33lenrecord = sum(field[1] for field in fieldspecs) + 1hdr = struct.pack('<BBBBLHH20x', ver, yr, mon, day, numrec, lenheader, lenrecord)f.write(hdr)# field specsfor 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)# terminatorf.write('\r')# recordsfor 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 filef.write('\x1A')

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Example calls

if name == 'main': import sys, csv from cStringIO import StringIO from operator import itemgetter

# Read a databasefilename = '/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 recordfieldnames, fieldspecs, records = db[0], db[1], db[2:]# Alter the databasedel records[4]records.sort(key=itemgetter(4))# Remove a fielddel fieldnames[0]del fieldspecs[0]records = [rec[1:] for rec in records]# Create a new DBFf = StringIO()dbfwriter(f, fieldnames, fieldspecs, records)# Read the data back from the new DBFprint '-' * 20    f.seek(0)for line in dbfreader(f):    print linef.close()# Convert to CSVprint '.' * 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_AMTMORNS ,555 ,1995-06-26,17.40SAWYH ,777 ,1995-06-29,97.30WALNG ,555 ,1995-05-22,173.40RATTC ,444 ,1995-06-23,185.80RITEB ,777 ,1995-06-02,560.40LAPLA ,111 ,1995-06-19,671.50MTIME ,333 ,1995-05-16,731.80OLDWO ,111 ,1995-07-14,863.96LILLO ,111 ,1995-07-03,909.91RATTC ,444 ,1995-06-12,1076.05MORNS ,444 ,1995-05-24,1405.00HIGHG ,111 ,1995-07-11,1984.83BMARK ,777 ,1995-05-18,3194.20FOODG ,333 ,1995-07-06,3401.32"""```