def _set_noconvert_columns(self):
names = self.orig_names<EOL>if self.usecols_dtype == '<STR_LIT>':<EOL><INDENT>usecols = list(self.usecols)<EOL>usecols.sort()<EOL><DEDENT>elif (callable(self.usecols) or<EOL>self.usecols_dtype not in ('<STR_LIT>', None)):<EOL><INDENT>usecols = self.names[:]<EOL><DEDENT>else:<EOL><INDENT>usecols = None<EOL><DEDENT>def _set(x):<EOL><INDENT>if usecols is not None and is_integer(x):<EOL><INDENT>x = usecols[x]<EOL><DEDENT>if not is_integer(x):<EOL><INDENT>x = names.index(x)<EOL><DEDENT>self._reader.set_noconvert(x)<EOL><DEDENT>if isinstance(self.parse_dates, list):<EOL><INDENT>for val in self.parse_dates:<EOL><INDENT>if isinstance(val, list):<EOL><INDENT>for k in val:<EOL><INDENT>_set(k)<EOL><DEDENT><DEDENT>else:<EOL><INDENT>_set(val)<EOL><DEDENT><DEDENT><DEDENT>elif isinstance(self.parse_dates, dict):<EOL><INDENT>for val in self.parse_dates.values():<EOL><INDENT>if isinstance(val, list):<EOL><INDENT>for k in val:<EOL><INDENT>_set(k)<EOL><DEDENT><DEDENT>else:<EOL><INDENT>_set(val)<EOL><DEDENT><DEDENT><DEDENT>elif self.parse_dates:<EOL><INDENT>if isinstance(self.index_col, list):<EOL><INDENT>for k in self.index_col:<EOL><INDENT>_set(k)<EOL><DEDENT><DEDENT>elif self.index_col is not None:<EOL><INDENT>_set(self.index_col)<EOL><DEDENT><DEDENT>
Set the columns that should not undergo dtype conversions.

Currently, any column that is involved with date parsing will not
undergo such conversions.