Astropy Glossary¶

(n,)

A parenthesized number followed by a comma denotes a tuple with one element. The trailing comma distinguishes a one-element tuple from a parenthesized n. This is from NumPy; see https://numpy.org/doc/stable/glossary.html.

number

Any numeric type. eg float or int or any of the numpy.number.

-like

Used to indicate on object of that type or that can instantiate the type. E.g. Quantity-like includes "2 * u.km" because astropy.units.Quantity("2 * u.km") works.

unit-like

Must be an UnitBase (subclass) instance or a string or other instance parseable by Unit.

quantity-like

Must be an Quantity (or subclass) instance or a string parseable by Quantity. Note that the interpretation of units in strings depends on the class – Quantity("180d") is 180 days, while Angle("180d") is 180 degrees – so check the string parses as intended for Quantity.

[‘physical type’]

The physical type of a quantity can be annotated in square brackets following a Quantity (or similar quantity-like).

For example, distance : quantity-like ['length']

angle-like

quantity-like, but interpreted by an angular SpecificTypeQuantity, like Angle or Longitude or Latitude. Note that the interpretation of units in strings depends on the class – Quantity("180d") is 180 days, while Angle("180d") is 180 degrees – so make sure the string parses as intended for Angle.

length-like

quantity-like, but interpretable by Distance.

frame-like

A BaseCoordinateFrame subclass instance or a string that can be converted to a Frame by _get_frame_class.

coordinate-like

A Coordinate-type object such as a BaseCoordinateFrame subclass instance or a SkyCoord (or subclass) instance.

table-like

An astropy Table or any object that can initialize one. Anything marked as table-like will be processed through a Table.

time-like

Time or any valid initializer.

buffer-like

Anything that implements Python’s buffer protocol. See https://docs.python.org/3/c-api/buffer.html#bufferobjects

writable file-like object

In the context of a file-like object object, anything that supports writing with a method write.