python读写dbf文件
发布时间:2020-12-17 17:23:00 所属栏目:Python 来源:网络整理
导读:今天PHP站长网 52php.cn把收集自互联网的代码分享给大家,仅供参考。 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 iterat
以下代码由PHP站长网 52php.cn收集自互联网 现在PHP站长网小编把它分享给大家,仅供参考
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,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_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 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,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 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,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_AMT MORNS,555,1995-06-26,17.40 SAWYH,777,1995-06-29,97.30 WALNG,1995-05-22,173.40 RATTC,444,1995-06-23,185.80 RITEB,1995-06-02,560.40 LAPLA,111,1995-06-19,671.50 MTIME,333,1995-05-16,731.80 OLDWO,1995-07-14,863.96 LILLO,1995-07-03,909.91 RATTC,1995-06-12,1076.05 MORNS,1995-05-24,1405.00 HIGHG,1995-07-11,1984.83 BMARK,1995-05-18,3194.20 FOODG,1995-07-06,3401.32 """ 以上内容由PHP站长网【52php.cn】收集整理供大家参考研究 如果以上内容对您有帮助,欢迎收藏、点赞、推荐、分享。 (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |