python读写dbf文件

概述python读写dbf文件

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读取遍历dBASE或Xbase文件中的记录。从Python的序列创建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,deci = struct.unpack('<11sc4xBB14x',f.read(32))        name = name.replace('','')       # eliminate Nuls from string           fIElds.append((name,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,deci),value in itertools.izip(fIElds,record):            if name == 'DeletionFlag':                continue            if typ == "N":                value = value.replace('','').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,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,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,day,numrec,lenheader,lenrecord)    f.write(hdr)                          # fIEld specs    for name,(typ,deci) in itertools.izip(fIEldnames,fIEldspecs):        name = name.ljust(11,'\x00')        fld = struct.pack('<11sc4xBB14x',name,deci)        f.write(fld)    # terminator    f.write('\r')    # records    for record in records:        f.write(' ')                        # deletion flag        for (typ,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 callsif __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,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,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,('D',8,('N',12,2)]['10005     ','WALNG      ','555        ',datetime.date(1995,5,22),Decimal("173.40")]['10004     ','BMARK      ','777        ',18),Decimal("3194.20")]['10029     ','SAWYH      ',6,29),Decimal("97.30")]['10013     ','RITEB      ',2),Decimal("560.40")]['10024     ','RATTC      ','444        ',21),Decimal("2223.50")]['10018     ',12),Decimal("1076.05")]['10025     ',23),Decimal("185.80")]['10038     ','olDWO      ','111        ',7,14),Decimal("863.96")]['10002     ','MTIME      ','333        ',16),Decimal("731.80")]['10007     ','MORNS      ',24),Decimal("1405.00")]['10026     ',26),Decimal("17.40")]['10030     ','liLLO      ',3),Decimal("909.91")]['10022     ','LAPLA      ',19),Decimal("671.50")]['10035     ','HIGHG      ',11),Decimal("1984.83")]['10033     ','FOODG      ',6),Decimal("3401.32")]--------------------['CUSTMR_ID',2)]['MORNS      ',Decimal("17.40")]['SAWYH      ',Decimal("97.30")]['WALNG      ',Decimal("173.40")]['RATTC      ',Decimal("185.80")]['RITEB      ',Decimal("560.40")]['LAPLA      ',Decimal("671.50")]['MTIME      ',Decimal("731.80")]['olDWO      ',Decimal("863.96")]['liLLO      ',Decimal("909.91")]['RATTC      ',Decimal("1076.05")]['MORNS      ',Decimal("1405.00")]['HIGHG      ',Decimal("1984.83")]['BMARK      ',Decimal("3194.20")]['FOODG      ',Decimal("3401.32")]....................CUSTMR_ID,EMPLOY_ID,ORDER_DATE,ORDER_AMTMORNS,555,1995-06-26,17.40SAWYH,777,1995-06-29,97.30WALNG,1995-05-22,173.40RATTC,444,1995-06-23,185.80RITEB,1995-06-02,560.40LAPLA,111,1995-06-19,671.50MTIME,333,1995-05-16,731.80olDWO,1995-07-14,863.96liLLO,1995-07-03,909.91RATTC,1995-06-12,1076.05MORNS,1995-05-24,1405.00HIGHG,1995-07-11,1984.83BMARK,1995-05-18,3194.20FOODG,1995-07-06,3401.32"""

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