new CSV file processing module - see PEP 305

Lib/csv/csv.py

@@ -0,0 +1,138 @@
+from _csv import Error, __version__, writer, reader, register_dialect, \
+                 unregister_dialect, get_dialect, list_dialects, \
+                 QUOTE_MINIMAL, QUOTE_ALL, QUOTE_NONNUMERIC, QUOTE_NONE, \
+                 __doc__
+
+__all__ = [ "QUOTE_MINIMAL", "QUOTE_ALL", "QUOTE_NONNUMERIC", "QUOTE_NONE",
+            "Error", "Dialect", "excel", "excel_tab", "reader", "writer",
+            "register_dialect", "get_dialect", "list_dialects",
+            "unregister_dialect", "__version__", "DictReader", "DictWriter" ]
+
+class Dialect:
+    _name = ""
+    _valid = False
+    # placeholders
+    delimiter = None
+    quotechar = None
+    escapechar = None
+    doublequote = None
+    skipinitialspace = None
+    lineterminator = None
+    quoting = None
+
+    def __init__(self):
+        if self.__class__ != Dialect:
+            self._valid = True
+        errors = self._validate()
+        if errors != []:
+            raise Error, "Dialect did not validate: %s" % ", ".join(errors)
+
+    def _validate(self):
+        errors = []
+        if not self._valid:
+            errors.append("can't directly instantiate Dialect class")
+
+        if self.delimiter is None:
+            errors.append("delimiter character not set")
+        elif (not isinstance(self.delimiter, str) or
+              len(self.delimiter) > 1):
+            errors.append("delimiter must be one-character string")
+
+        if self.quotechar is None:
+            if self.quoting != QUOTE_NONE:
+                errors.append("quotechar not set")
+        elif (not isinstance(self.quotechar, str) or
+              len(self.quotechar) > 1):
+            errors.append("quotechar must be one-character string")
+
+        if self.lineterminator is None:
+            errors.append("lineterminator not set")
+        elif not isinstance(self.lineterminator, str):
+            errors.append("lineterminator must be a string")
+
+        if self.doublequote not in (True, False):
+            errors.append("doublequote parameter must be True or False")
+
+        if self.skipinitialspace not in (True, False):
+            errors.append("skipinitialspace parameter must be True or False")
+
+        if self.quoting is None:
+            errors.append("quoting parameter not set")
+
+        if self.quoting is QUOTE_NONE:
+            if (not isinstance(self.escapechar, (unicode, str)) or
+                len(self.escapechar) > 1):
+                errors.append("escapechar must be a one-character string or unicode object")
+
+        return errors
+
+class excel(Dialect):
+    delimiter = ','
+    quotechar = '"'
+    doublequote = True
+    skipinitialspace = False
+    lineterminator = '\r\n'
+    quoting = QUOTE_MINIMAL
+register_dialect("excel", excel)
+
+class excel_tab(excel):
+    delimiter = '\t'
+register_dialect("excel-tab", excel_tab)
+
+
+class DictReader:
+    def __init__(self, f, fieldnames, restkey=None, restval=None,
+                 dialect="excel", *args):
+        self.fieldnames = fieldnames    # list of keys for the dict
+        self.restkey = restkey          # key to catch long rows
+        self.restval = restval          # default value for short rows
+        self.reader = reader(f, dialect, *args)
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        row = self.reader.next()
+        # unlike the basic reader, we prefer not to return blanks,
+        # because we will typically wind up with a dict full of None
+        # values
+        while row == []:
+            row = self.reader.next()
+        d = dict(zip(self.fieldnames, row))
+        lf = len(self.fieldnames)
+        lr = len(row)
+        if lf < lr:
+            d[self.restkey] = row[lf:]
+        elif lf > lr:
+            for key in self.fieldnames[lr:]:
+                d[key] = self.restval
+        return d
+
+
+class DictWriter:
+    def __init__(self, f, fieldnames, restval="", extrasaction="raise",
+                 dialect="excel", *args):
+        self.fieldnames = fieldnames    # list of keys for the dict
+        self.restval = restval          # for writing short dicts
+        if extrasaction.lower() not in ("raise", "ignore"):
+            raise ValueError, \
+                  ("extrasaction (%s) must be 'raise' or 'ignore'" % 
+                   extrasaction)
+        self.extrasaction = extrasaction
+        self.writer = writer(f, dialect, *args)
+
+    def _dict_to_list(self, rowdict):
+        if self.extrasaction == "raise":
+            for k in rowdict.keys():
+                if k not in self.fieldnames:
+                    raise ValueError, "dict contains fields not in fieldnames"
+        return [rowdict.get(key, self.restval) for key in self.fieldnames] 
+
+    def writerow(self, rowdict):
+        return self.writer.writerow(self._dict_to_list(rowdict))
+
+    def writerows(self, rowdicts):
+        rows = []
+        for rowdict in rowdicts:
+            rows.append(self._dict_to_list(rowdict))
+        return self.writer.writerows(rows)