Method: Polars::Functions#col

Defined in:
lib/polars/functions/col.rb

#col(name, *more_names) ⇒ Expr

Return an expression representing a column in a DataFrame.

Returns:



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# File 'lib/polars/functions/col.rb', line 6

def col(name, *more_names)
  if more_names.any?
    if Utils.strlike?(name)
      names_str = [name]
      names_str.concat(more_names)
      return Selector._by_name(names_str.map(&:to_s), strict: true, expand_patterns: true).as_expr
    elsif Utils.is_polars_dtype(name)
      dtypes = [name]
      dtypes.concat(more_names)
      return Selector._by_type(dtypes).as_expr
    else
      msg = "invalid input for `col`\n\nExpected `str` or `DataType`, got #{name.class.name}."
      raise TypeError, msg
    end
  end

  if Utils.strlike?(name)
    Utils.wrap_expr(Plr.col(name.to_s))
  elsif Utils.is_polars_dtype(name)
    dtypes = [name]
    Selector._by_dtype(dtypes).as_expr
  elsif name.is_a?(::Array) || name.is_a?(::Set)
    names = Array(name)
    if names.empty?
      return Utils.wrap_expr(Plr.cols(names))
    end

    item = names[0]
    if Utils.strlike?(item)
      Selector._by_name(names.map(&:to_s), strict: true, expand_patterns: true).as_expr
    elsif Utils.is_polars_dtype(item)
      Selector._by_dtype(names).as_expr
    else
      msg = "invalid input for `col`\n\nExpected iterable of type `str` or `DataType`, got iterable of type #{item.class.name}."
      raise TypeError, msg
    end
  else
    msg = "invalid input for `col`\n\nExpected `str` or `DataType`, got #{name.class.name}."
    raise TypeError, msg
  end
end