122 lines
4.3 KiB
Python
122 lines
4.3 KiB
Python
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import struct, datetime, decimal, itertools
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def dbfreader(f):
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"""Returns an iterator over records in a Xbase DBF file.
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The first row returned contains the field names.
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The second row contains field specs: (type, size, decimal places).
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Subsequent rows contain the data records.
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If a record is marked as deleted, it is skipped.
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File should be opened for binary reads.
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"""
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# See DBF format spec at:
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# http://www.pgts.com.au/download/public/xbase.htm#DBF_STRUCT
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numrec, lenheader = struct.unpack('<xxxxLH22x', f.read(32))
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numfields = (lenheader - 33) // 32
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fields = []
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for fieldno in range(numfields):
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name, typ, size, deci = struct.unpack('<11sc4xBB14x', f.read(32))
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name = name.replace('\0', '') # eliminate NULs from string
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fields.append((name, typ, size, deci))
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yield [field[0] for field in fields]
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yield [tuple(field[1:]) for field in fields]
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terminator = f.read(1)
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assert terminator == '\r'
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fields.insert(0, ('DeletionFlag', 'C', 1, 0))
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fmt = ''.join(['%ds' % fieldinfo[2] for fieldinfo in fields])
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fmtsiz = struct.calcsize(fmt)
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for i in range(numrec):
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record = struct.unpack(fmt, f.read(fmtsiz))
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if record[0] != ' ':
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continue # deleted record
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result = []
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for (name, typ, size, deci), value in zip(fields, record):
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if name == 'DeletionFlag':
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continue
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if typ == "N":
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value = value.replace('\0', '').lstrip()
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if value == '':
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value = 0
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elif deci:
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try:
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value = decimal.Decimal(value)
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except decimal.InvalidOperation:
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# Could be '************************' (for NULL)
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value = 0
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else:
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value = value
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elif typ == 'D':
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y, m, d = int(value[:4]), int(value[4:6]), int(value[6:8])
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try:
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value = datetime.date(y, m, d)
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except ValueError:
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# Could be '00000000' (for NULL)
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value = 0
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elif typ == 'L':
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value = (value in 'YyTt' and 'T') or (value in 'NnFf' and 'F') or '?'
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result.append(value)
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yield result
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def dbfwriter(f, fieldnames, fieldspecs, records):
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""" Return a string suitable for writing directly to a binary dbf file.
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File f should be open for writing in a binary mode.
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Fieldnames should be no longer than ten characters and not include \x00.
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Fieldspecs are in the form (type, size, deci) where
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type is one of:
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C for ascii character data
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M for ascii character memo data (real memo fields not supported)
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D for datetime objects
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N for ints or decimal objects
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L for logical values 'T', 'F', or '?'
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size is the field width
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deci is the number of decimal places in the provided decimal object
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Records can be an iterable over the records (sequences of field values).
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"""
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# header info
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ver = 3
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now = datetime.datetime.now()
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yr, mon, day = now.year-1900, now.month, now.day
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numrec = len(records)
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numfields = len(fieldspecs)
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lenheader = numfields * 32 + 33
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lenrecord = sum(field[1] for field in fieldspecs) + 1
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hdr = struct.pack('<BBBBLHH20x', ver, yr, mon, day, numrec, lenheader, lenrecord)
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f.write(hdr)
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# field specs
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for name, (typ, size, deci) in zip(fieldnames, fieldspecs):
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name = name.ljust(11, '\x00')
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fld = struct.pack('<11sc4xBB14x', name, typ, size, deci)
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f.write(fld)
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# terminator
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f.write('\r')
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# records
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for record in records:
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f.write(' ') # deletion flag
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for (typ, size, deci), value in zip(fieldspecs, record):
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if typ == "N":
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value = str(value).rjust(size, ' ')
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elif typ == 'D':
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value = value.strftime('%Y%m%d')
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elif typ == 'L':
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value = str(value)[0].upper()
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else:
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value = str(value)[:size].ljust(size, ' ')
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assert len(value) == size
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f.write(value)
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# End of file
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f.write('\x1A')
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