packages/vaex-core/vaex/dataframe.py
def add_virtual_column(self, name, expression, unique=False):
        """Add a virtual column to the DataFrame.

        Example:

        >>> df.add_virtual_column("r", "sqrt(x**2 + y**2 + z**2)")
        >>> df.select("r < 10")

        :param: str name: name of virtual column
        :param: expression: expression for the column
        :param str unique: if name is already used, make it unique by adding a postfix, e.g. _1, or _2
        """
        type = "change" if name in self.virtual_columns else "add"
        expression = _ensure_string_from_expression(expression)
        if name in self.get_column_names(virtual=False):
            renamed = '__' +vaex.utils.find_valid_name(name, used=self.get_column_names())
            expression = self._rename(name, renamed, expression)[0].expression

        name = vaex.utils.find_valid_name(name, used=[] if not unique else self.get_column_names())
        self.virtual_columns[name] = expression
        self.column_names.append(name)
        self._save_assign_expression(name)
        self.signal_column_changed.emit(self, name, "add")
def add_virtual_column(self, name, expression, unique=False):
        type = "change" if name in self.virtual_columns else "add"
        expression = _ensure_string_from_expression(expression)
        if name in self.get_column_names(virtual=False):
            renamed = '__' +vaex.utils.find_valid_name(name, used=self.get_column_names())
            expression = self._rename(name, renamed, expression)[0].expression

        name = vaex.utils.find_valid_name(name, used=[] if not unique else self.get_column_names())
        self.virtual_columns[name] = expression
        self.column_names.append(name)
        self._save_assign_expression(name)
        self.signal_column_changed.emit(self, name, "add")
def add_virtual_column ( self , name , expression , unique = False ) : type = "change" if name in self . virtual_columns else "add" expression = _ensure_string_from_expression ( expression ) if name in self . get_column_names ( virtual = False ) : renamed = '__' + vaex . utils . find_valid_name ( name , used = self . get_column_names ( ) ) expression = self . _rename ( name , renamed , expression ) [ 0 ] . expression name = vaex . utils . find_valid_name ( name , used = [ ] if not unique else self . get_column_names ( ) ) self . virtual_columns [ name ] = expression self . column_names . append ( name ) self . _save_assign_expression ( name ) self . signal_column_changed . emit ( self , name , "add" )
Add a virtual column to the DataFrame.

        Example:

        >>> df.add_virtual_column("r", "sqrt(x**2 + y**2 + z**2)")
        >>> df.select("r < 10")

        :param: str name: name of virtual column
        :param: expression: expression for the column
        :param str unique: if name is already used, make it unique by adding a postfix, e.g. _1, or _2
Add a virtual column to the DataFrame .