/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/table.py
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revision 590 by bh, Wed Apr 2 15:03:19 2003 UTC revision 984 by bh, Thu May 22 16:37:48 2003 UTC
# Line 1  Line 1 
1  # Copyright (c) 2001, 2002, 2003 by Intevation GmbH  # Copyright (c) 2001, 2002, 2003 by Intevation GmbH
2  # Authors:  # Authors:
3  # Bernhard Herzog <[email protected]>  # Bernhard Herzog <[email protected]>
4    # Jan-Oliver Wagner <[email protected]>
5  #  #
6  # This program is free software under the GPL (>=v2)  # This program is free software under the GPL (>=v2)
7  # Read the file COPYING coming with Thuban for details.  # Read the file COPYING coming with Thuban for details.
# Line 11  Classes for handling tables of data. Line 12  Classes for handling tables of data.
12    
13  __version__ = "$Revision$"  __version__ = "$Revision$"
14    
15    import inspect
16    import warnings
17    
18  import dbflib  import dbflib
19    
20  # the field types supported by a Table instance.  # the field types supported by a Table instance.
# Line 24  dbflib_fieldtypes = {dbflib.FTString: FI Line 28  dbflib_fieldtypes = {dbflib.FTString: FI
28                       dbflib.FTInteger: FIELDTYPE_INT,                       dbflib.FTInteger: FIELDTYPE_INT,
29                       dbflib.FTDouble: FIELDTYPE_DOUBLE}                       dbflib.FTDouble: FIELDTYPE_DOUBLE}
30    
 class Table:  
31    
32    class OldTableInterfaceMixin:
33    
34        """Mixin to implement the old table interface using the new one"""
35    
36        def __deprecation_warning(self):
37            """Issue a DeprecationWarning for code hat uses the old interface"""
38            callername = inspect.currentframe().f_back.f_code.co_name
39            warnings.warn("The %s method of the old table interface"
40                          " is deprecated" % callername,
41                          DeprecationWarning, stacklevel = 3)
42    
43        def record_count(self):
44            self.__deprecation_warning()
45            return self.NumRows()
46    
47        def field_count(self):
48            self.__deprecation_warning()
49            return self.NumColumns()
50    
51        def field_info(self, field):
52            """Return a tuple (type, name, width, prec) for the field no. field
53    
54            type is the data type of the field, name the name, width the
55            field width in characters and prec the decimal precision. width
56            and prec will be zero if the information returned by the Column
57            method doesn't provide values for them.
58            """
59            self.__deprecation_warning()
60            col = self.Column(field)
61            return (col.type, col.name,
62                   getattr(col, "width", 0), getattr(col, "prec", 0))
63    
64        def field_info_by_name(self, col):
65            self.__deprecation_warning()
66            try:
67                return self.field_info(col)
68            except KeyError:
69                # FIXME: It may be that field_info raises other exceptions
70                # when the name is not a valid column name.
71                return None
72    
73        def field_range(self, fieldName):
74            self.__deprecation_warning()
75            min, max = self.ValueRange(fieldName)
76            return ((min, None), (max, None))
77    
78        def GetUniqueValues(self, field):
79            self.__deprecation_warning()
80            return self.UniqueValues(field)
81    
82        def read_record(self, r):
83            self.__deprecation_warning()
84            return self.ReadRowAsDict(r)
85    
86    
87    
88    class DBFColumn:
89    
90        """Description of a column in a DBFTable
91    
92        Instances have the following public attributes:
93    
94        name -- Name of the column
95        type -- Type of the column (one of FIELDTYPE_STRING, FIELDTYPE_INT or\
96                FIELDTYPE_DOUBLE)
97        index -- The index of the column
98        width -- the width of the data in the column
99        prec -- The precision of the data (only valid for type == FIELDTYPE_DOUBLE)
100      """      """
     Represent a table of data.  
101    
102      Currently this is basically just a wrapper around dbflib.      def __init__(self, name, type, width, prec, index):
103            self.name = name
104            self.type = type
105            self.width = width
106            self.prec = prec
107            self.index = index
108    
109    
110    class DBFTable(OldTableInterfaceMixin):
111    
112        """
113        Table interface for the data in a DBF file
114      """      """
115    
116      # Implementation strategy regarding writing to a DBF file:      # Implementation strategy regarding writing to a DBF file:
# Line 53  class Table: Line 134  class Table:
134          # If true, self.dbf is open for writing.          # If true, self.dbf is open for writing.
135          self._writable = 0          self._writable = 0
136    
137      def Destroy(self):          # Create the column information objects
138          self.dbf.close()          self.columns = []
139          self.dbf = None          self.column_map = {}
140            for i in range(self.NumColumns()):
141                ftype, name, width, prec = self.dbf.field_info(i)
142                ftype = dbflib_fieldtypes[ftype]
143                index = len(self.columns)
144                col = DBFColumn(name, ftype, width, prec, index)
145                self.columns.append(col)
146                self.column_map[name] = col
147                self.column_map[index] = col
148    
149      def record_count(self):      def NumRows(self):
150          """Return the number of records"""          """Return the number of rows in the table"""
151          return self.dbf.record_count()          return self.dbf.record_count()
152    
153      def field_count(self):      def NumColumns(self):
154          """Return the number of fields in a record"""          """Return the number of columns in the table"""
155          return self.dbf.field_count()          return self.dbf.field_count()
156    
157      def field_info(self, field):      def Columns(self):
158          """Return a tuple (type, name, width, prec) for the field no. field          """Return the table's colum definitions
159    
160          type is the data type of the field, name the name, width the          The return value is a sequence of DBFColumn instances, one for
161          field width in characters and prec the decimal precision.          each column.
162          """          """
163          type, name, width, prec = self.dbf.field_info(field)          return self.columns
164          type = dbflib_fieldtypes[type]  
165          return type, name, width, prec      def Column(self, col):
166            """Return information about the column given by its name or index
167    
168      def field_info_by_name(self, fieldName):          The returned object is an instance of DBFColumn
169          count = self.field_count()          """
170            return self.column_map[col]
171    
172        def HasColumn(self, col):
173            """Return whether the table has a column with the given name or index
174            """
175            return self.column_map.has_key(col)
176    
177          for i in range(count):      def ReadRowAsDict(self, row):
178              info = self.field_info(i)          """Return the entire row as a dictionary with column names as keys"""
179              if info[1] == fieldName:          return self.dbf.read_record(row)
                 return info  
180    
181          return None      def ReadValue(self, row, col):
182            """Return the value of the specified row and column
183    
184      def read_record(self, record):          The col parameter may be the index of the column or its name.
         """Return the record no. record as a dict mapping field names to values  
185          """          """
186          return self.dbf.read_record(record)          return self.dbf.read_record(row)[self.column_map[col].name]
187    
188        def ValueRange(self, col):
189            """Return the minimum and maximum values of the values in the column
190    
191            The return value is a tuple (min, max) unless the table is empty
192            in which case the return value is None.
193            """
194            count = self.NumRows()
195    
196            if count == 0:
197                return None
198    
199            min = max = self.ReadValue(0, col)
200            for i in range(1, count):
201                value = self.ReadValue(i, col)
202                if value < min:
203                    min = value
204                elif value > max:
205                    max = value
206    
207            return (min, max)
208    
209        def UniqueValues(self, col):
210            """Return a sorted list of all unique values in the column col"""
211            dict = {}
212    
213            for i in range(self.NumRows()):
214                value = self.ReadValue(i, col)
215                dict[value] = 0
216    
217            values = dict.keys()
218            values.sort()
219            return values
220    
221        def Dependencies(self):
222            """Return an empty sequence. The DBFTable doesn't depend on anything"""
223            return ()
224    
225        # DBF specific interface parts.
226    
227        def Destroy(self):
228            self.dbf.close()
229            self.dbf = None
230    
231      def write_record(self, record, values):      def write_record(self, record, values):
232          """Write the values into the record          """Write the values into the record
# Line 111  class Table: Line 249  class Table:
249          self.dbf.write_record(record, values)          self.dbf.write_record(record, values)
250          self.dbf.commit()          self.dbf.commit()
251    
252    
253    
254    class MemoryColumn:
255    
256        def __init__(self, name, type, index):
257            self.name = name
258            self.type = type
259            self.index = index
260    
261    class MemoryTable(OldTableInterfaceMixin):
262    
263        """Very simple table implementation that operates on a list of tuples"""
264    
265        def __init__(self, fields, data):
266            """Initialize the MemoryTable
267    
268            Parameters:
269            fields -- List of (name, field_type) pairs
270            data -- List of tuples, one for each row of data
271            """
272            self.data = data
273    
274            # Create the column information objects
275            self.columns = []
276            self.column_map = {}
277            for name, ftype in fields:
278                index = len(self.columns)
279                col = MemoryColumn(name, ftype, index)
280                self.columns.append(col)
281                self.column_map[name] = col
282                self.column_map[index] = col
283    
284        def NumColumns(self):
285            """Return the number of columns in the table"""
286            return len(self.columns)
287    
288        def Column(self, col):
289            """Return information about the column given by its name or index
290    
291            The returned object is an instance of MemoryColumn.
292            """
293            return self.column_map[col]
294    
295        def Columns(self):
296            """Return the table's colum definitions
297    
298            The return value is a sequence of MemoryColumn instances, one
299            for each column.
300            """
301            return self.columns
302    
303        def HasColumn(self, col):
304            """Return whether the table has a column with the given name or index
305            """
306            return self.column_map.has_key(col)
307    
308        def NumRows(self):
309            """Return the number of rows in the table"""
310            return len(self.data)
311    
312        def ReadValue(self, row, col):
313            """Return the value of the specified row and column
314    
315            The col parameter may be the index of the column or its name.
316            """
317            return self.data[row][self.column_map[col].index]
318    
319        def ReadRowAsDict(self, index):
320            """Return the entire row as a dictionary with column names as keys"""
321            return dict([(col.name, self.data[index][col.index])
322                          for col in self.columns])
323    
324        def ValueRange(self, col):
325            """Return the minimum and maximum values of the values in the column
326    
327            The return value is a tuple (min, max) unless the table is empty
328            in which case the return value is None.
329            """
330    
331            index = self.column_map[col].index
332            values = [row[index] for row in self.data]
333            if not values:
334                return None
335    
336            return min(values), max(values)
337    
338        def UniqueValues(self, col):
339            """Return a sorted list of all unique values in the column col"""
340            dict = {}
341    
342            for i in range(self.NumRows()):
343                value = self.ReadValue(i, col)
344                dict[value] = 0
345    
346            values = dict.keys()
347            values.sort()
348            return values
349    
350        def Dependencies(self):
351            """Return an empty sequence. The MemoryTable doesn't depend on anything
352            """
353            return ()
354    
355        def write_record(self, record, values):
356            # TODO: Check for correct lenght and perhaps also
357            # for correct types in case values is a tuple. How to report problems?
358            # TODO: Allow values to be a dictionary and write the single
359            # fields that are specified.
360            self.data[record] = values
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