/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/table.py
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revision 284 by bh, Tue Aug 27 14:08:32 2002 UTC revision 590 by bh, Wed Apr 2 15:03:19 2003 UTC
# Line 1  Line 1 
1  # Copyright (c) 2001, 2002 by Intevation GmbH  # Copyright (c) 2001, 2002, 2003 by Intevation GmbH
2  # Authors:  # Authors:
3  # Bernhard Herzog <[email protected]>  # Bernhard Herzog <[email protected]>
4  #  #
# Line 32  class Table: Line 32  class Table:
32      Currently this is basically just a wrapper around dbflib.      Currently this is basically just a wrapper around dbflib.
33      """      """
34    
35        # Implementation strategy regarding writing to a DBF file:
36        #
37        # Most of the time Thuban only needs to read from a table and it is
38        # important that Thuban can work with read-only files. Therefore the
39        # DBF file is opened only for reading initially. Only when
40        # write_record is called we try to open the DBF file for writing as
41        # well. If that succeeds the read/write DBF file will be used for
42        # all IO afterwards.
43        #
44        # It's important to use the same DBF file object for both reading
45        # and writing to make sure that reading a records after writing
46        # returns the new values. With two separate objects this wouldn't
47        # work because a DBF file object buffers some data
48    
49      def __init__(self, filename):      def __init__(self, filename):
50          self.filename = filename          self.filename = filename
51          self.dbf = dbflib.DBFFile(filename)          self.dbf = dbflib.DBFFile(filename)
52    
53            # If true, self.dbf is open for writing.
54            self._writable = 0
55    
56      def Destroy(self):      def Destroy(self):
57          self.dbf.close()          self.dbf.close()
58          self.dbf = None          self.dbf = None
# Line 58  class Table: Line 75  class Table:
75          type = dbflib_fieldtypes[type]          type = dbflib_fieldtypes[type]
76          return type, name, width, prec          return type, name, width, prec
77    
78        def field_info_by_name(self, fieldName):
79            count = self.field_count()
80    
81            for i in range(count):
82                info = self.field_info(i)
83                if info[1] == fieldName:
84                    return info
85    
86            return None
87    
88      def read_record(self, record):      def read_record(self, record):
89          """Return the record no. record as a dict mapping field names to values          """Return the record no. record as a dict mapping field names to values
90          """          """
# Line 76  class Table: Line 103  class Table:
103          If it's a sequence, all fields must be present in the right          If it's a sequence, all fields must be present in the right
104          order.          order.
105          """          """
106          writable_dbf = dbflib.DBFFile(self.filename, "r+b")          if not self._writable:
107          writable_dbf.write_record(record, values)              new_dbf = dbflib.DBFFile(self.filename, "r+b")
108          writable_dbf.close()              self.dbf.close()
109                self.dbf = new_dbf
110                self._writable = 1
111            self.dbf.write_record(record, values)
112            self.dbf.commit()
113    
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