/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/table.py
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revision 806 by jan, Fri May 2 16:43:59 2003 UTC revision 839 by bh, Tue May 6 15:54:18 2003 UTC
# Line 12  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 25  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 MemoryTable:  
31    
32      """Quite simple table implementation that operates on a list of tuples.  class OldTableInterfaceMixin:
     All of the data are kept in the memory."""  
33    
34      def __init__(self, fields, data):      """Mixin to implement the old table interface using the new one"""
         """Initialize the MemoryTable  
35    
36          Parameters:      def __deprecation_warning(self):
37          fields -- List of (name, field_type) pairs          """Issue a DeprecationWarning for code hat uses the old interface"""
38          data -- List of tuples, one for each row of data          callername = inspect.currentframe().f_back.f_code.co_name
39          """          warnings.warn("The %s method of the old table interface"
40          self.fields = fields                        " is deprecated" % callername,
41          self.data = data                        DeprecationWarning, stacklevel = 3)
42    
43        def record_count(self):
44            self.__deprecation_warning()
45            return self.NumRows()
46    
47      def field_count(self):      def field_count(self):
48          return len(self.fields)          self.__deprecation_warning()
49            return self.NumColumns()
50    
51      def field_info(self, index):      def field_info(self, field):
52          name, type = self.fields[index]          """Return a tuple (type, name, width, prec) for the field no. field
         return (type, name)  
53    
54      def record_count(self):          type is the data type of the field, name the name, width the
55          return len(self.data)          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 read_record(self, index):      def field_range(self, fieldName):
74          return dict([(self.fields[i][0], self.data[index][i])          self.__deprecation_warning()
75                        for i in range(len(self.fields))])          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    
     def write_record(self, record, values):  
         # TODO: Check for correct lenght and perhaps also  
         # for correct types in case values is a tuple. How to report problems?  
         # TODO: Allow values to be a dictionary and write the single  
         # fields that are specified.  
         self.data[record] = values  
86    
87    
88  class DBFTable:  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        """
101    
102        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      Table interface for the data in a DBF file
# Line 89  class DBFTable: Line 134  class DBFTable:
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
         type = dbflib_fieldtypes[type]  
         return type, name, width, prec  
   
     def field_info_by_name(self, fieldName):  
         count = self.field_count()  
   
         for i in range(count):  
             info = self.field_info(i)  
             if info[1] == fieldName:  
                 return info  
164    
165          return None      def Column(self, col):
166            """Return information about the column given by its name or index
167    
168      def field_range(self, fieldName):          The returned object is an instance of DBFColumn
169          """Finds the first occurences of the minimum and maximum values          """
170          in the table for the given field.          return self.column_map[col]
171    
172          This assumes that the standard comparison operators (<, >, etc.)      def HasColumn(self, col):
173          will work for the given data.          """Return whether the table has a column with the given name or index
174            """
175            return self.column_map.has_key(col)
176    
177          Returns a tuple ((min, rec), (max, rec)) where:      def ReadRowAsDict(self, row):
178              min is the minimum value          """Return the entire row as a dictionary with column names as keys"""
179              max is the maximum value          return self.dbf.read_record(row)
             rec is the record number where the value was found. One  
                 should check that the record number of min is not  
                 the same as the record number of max.  
180    
181          Returns None if there are no records      def ReadValue(self, row, col):
182            """Return the value of the specified row and column
183    
184            The col parameter may be the index of the column or its name.
185          """          """
186            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          count = self.record_count()          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:          if count == 0:
197              return None              return None
198    
199          rec = self.read_record(0)          min = max = self.ReadValue(0, col)
   
         min = rec[fieldName]  
         min_rec = 0  
   
         max = rec[fieldName]  
         max_rec = 0  
   
200          for i in range(1, count):          for i in range(1, count):
201              rec = self.read_record(i)              value = self.ReadValue(i, col)
202              data = rec[fieldName]              if value < min:
203                    min = value
204                elif value > max:
205                    max = value
206    
207              if data < min:          return (min, max)
                 min = data  
                 min_rec = rec  
             elif data > max:  
                 max = data  
                 max_rec = rec  
   
         return ((min, min_rec), (max, max_rec))  
   
     def GetUniqueValues(self, fieldName):  
         """Return a list of all unique entries in the table for the given  
         field name.  
         """  
208    
209        def UniqueValues(self, col):
210            """Return a sorted list of all unique values in the column col"""
211          dict = {}          dict = {}
212    
213          for i in range(0, self.record_count()):          for i in range(self.NumRows()):
214              rec = self.read_record(i)              value = self.ReadValue(i, col)
215              data = rec[fieldName]              dict[value] = 0
216    
217              if not dict.has_key(data):          values = dict.keys()
218                  dict[data] = 0          values.sort()
219            return values
220    
         return dict.keys()  
221    
222      def read_record(self, record):      # DBF specific interface parts.
223          """Return the record no. record as a dict mapping field names to values  
224          """      def Destroy(self):
225          return self.dbf.read_record(record)          self.dbf.close()
226            self.dbf = None
227    
228      def write_record(self, record, values):      def write_record(self, record, values):
229          """Write the values into the record          """Write the values into the record
# Line 212  class DBFTable: Line 250  class DBFTable:
250    
251  # Temporary backwards compatibility  # Temporary backwards compatibility
252  Table = DBFTable  Table = DBFTable
253    
254    
255    
256    class MemoryColumn:
257    
258        def __init__(self, name, type, index):
259            self.name = name
260            self.type = type
261            self.index = index
262    
263    class MemoryTable(OldTableInterfaceMixin):
264    
265        """Very simple table implementation that operates on a list of tuples"""
266    
267        def __init__(self, fields, data):
268            """Initialize the MemoryTable
269    
270            Parameters:
271            fields -- List of (name, field_type) pairs
272            data -- List of tuples, one for each row of data
273            """
274            self.data = data
275    
276            # Create the column information objects
277            self.columns = []
278            self.column_map = {}
279            for name, ftype in fields:
280                index = len(self.columns)
281                col = MemoryColumn(name, ftype, index)
282                self.columns.append(col)
283                self.column_map[name] = col
284                self.column_map[index] = col
285    
286        def NumColumns(self):
287            """Return the number of columns in the table"""
288            return len(self.columns)
289    
290        def Column(self, col):
291            """Return information about the column given by its name or index
292    
293            The returned object is an instance of MemoryColumn.
294            """
295            return self.column_map[col]
296    
297        def Columns(self):
298            """Return the table's colum definitions
299    
300            The return value is a sequence of MemoryColumn instances, one
301            for each column.
302            """
303            return self.columns
304    
305        def HasColumn(self, col):
306            """Return whether the table has a column with the given name or index
307            """
308            return self.column_map.has_key(col)
309    
310        def NumRows(self):
311            """Return the number of rows in the table"""
312            return len(self.data)
313    
314        def ReadValue(self, row, col):
315            """Return the value of the specified row and column
316    
317            The col parameter may be the index of the column or its name.
318            """
319            return self.data[row][self.column_map[col].index]
320    
321        def ReadRowAsDict(self, index):
322            """Return the entire row as a dictionary with column names as keys"""
323            return dict([(col.name, self.data[index][col.index])
324                          for col in self.columns])
325    
326        def ValueRange(self, col):
327            """Return the minimum and maximum values of the values in the column
328    
329            The return value is a tuple (min, max) unless the table is empty
330            in which case the return value is None.
331            """
332    
333            index = self.column_map[col].index
334            values = [row[index] for row in self.data]
335            if not values:
336                return None
337    
338            return min(values), max(values)
339    
340        def UniqueValues(self, col):
341            """Return a sorted list of all unique values in the column col"""
342            dict = {}
343    
344            for i in range(self.NumRows()):
345                value = self.ReadValue(i, col)
346                dict[value] = 0
347    
348            values = dict.keys()
349            values.sort()
350            return values
351    
352    
353        def write_record(self, record, values):
354            # TODO: Check for correct lenght and perhaps also
355            # for correct types in case values is a tuple. How to report problems?
356            # TODO: Allow values to be a dictionary and write the single
357            # fields that are specified.
358            self.data[record] = values
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