Column¶
-
class
astropy.table.
Column
[source] [edit on github]¶ Bases:
astropy.table.column.BaseColumn
Define a data column for use in a Table object.
Parameters: - data : list, ndarray or None
Column data values
- name : str
Column name and key for reference within Table
- dtype : numpy.dtype compatible value
Data type for column
- shape : tuple or ()
Dimensions of a single row element in the column data
- length : int or 0
Number of row elements in column data
- description : str or None
Full description of column
- unit : str or None
Physical unit
- format : str or None or function or callable
Format string for outputting column values. This can be an “old-style” (
format % value
) or “new-style” (str.format
) format specification string or a function or any callable object that accepts a single value and returns a string.- meta : dict-like or None
Meta-data associated with the column
Examples
A Column can be created in two different ways:
Provide a
data
value but notshape
orlength
(which are inferred from the data).Examples:
col = Column(data=[1, 2], name='name') # shape=(2,) col = Column(data=[[1, 2], [3, 4]], name='name') # shape=(2, 2) col = Column(data=[1, 2], name='name', dtype=float) col = Column(data=np.array([1, 2]), name='name') col = Column(data=['hello', 'world'], name='name')
The
dtype
argument can be any value which is an acceptable fixed-size data-type initializer for the numpy.dtype() method. See https://docs.scipy.org/doc/numpy/reference/arrays.dtypes.html. Examples include:- Python non-string type (float, int, bool)
- Numpy non-string type (e.g. np.float32, np.int64, np.bool_)
- Numpy.dtype array-protocol type strings (e.g. ‘i4’, ‘f8’, ‘S15’)
If no
dtype
value is provide then the type is inferred usingnp.array(data)
.Provide
length
and optionallyshape
, but notdata
Examples:
col = Column(name='name', length=5) col = Column(name='name', dtype=int, length=10, shape=(3,4))
The default
dtype
isnp.float64
. Theshape
argument is the array shape of a single cell in the column.
Attributes Summary
name
The name of this column. quantity
A view of this table column as a Quantity
object with units given by the Column’sunit
parameter.unit
The unit associated with this column. Methods Summary
convert_unit_to
(new_unit[, equivalencies])Converts the values of the column in-place from the current unit to the given unit. copy
([order, data, copy_data])Return a copy of the current instance. insert
(obj, values[, axis])Insert values before the given indices in the column and return a new Column
object.more
([max_lines, show_name, show_unit])Interactively browse column with a paging interface. pformat
([max_lines, show_name, show_unit, …])Return a list of formatted string representation of column values. pprint
([max_lines, show_name, show_unit, …])Print a formatted string representation of column values. to
(unit[, equivalencies])Converts this table column to a Quantity
object with the requested units.Attributes Documentation
-
name
¶ The name of this column.
-
quantity
¶ A view of this table column as a
Quantity
object with units given by the Column’sunit
parameter.
-
unit
¶ The unit associated with this column. May be a string or a
astropy.units.UnitBase
instance.Setting the
unit
property does not change the values of the data. To perform a unit conversion, useconvert_unit_to
.
Methods Documentation
-
convert_unit_to
(new_unit, equivalencies=[]) [edit on github]¶ Converts the values of the column in-place from the current unit to the given unit.
To change the unit associated with this column without actually changing the data values, simply set the
unit
property.Parameters: - new_unit : str or
astropy.units.UnitBase
instance The unit to convert to.
- equivalencies : list of equivalence pairs, optional
A list of equivalence pairs to try if the unit are not directly convertible. See Equivalencies.
Raises: - astropy.units.UnitsError
If units are inconsistent
- new_unit : str or
-
copy
(order='C', data=None, copy_data=True) [edit on github]¶ Return a copy of the current instance.
If
data
is supplied then a view (reference) ofdata
is used, andcopy_data
is ignored.Parameters: - order : {‘C’, ‘F’, ‘A’, ‘K’}, optional
Controls the memory layout of the copy. ‘C’ means C-order, ‘F’ means F-order, ‘A’ means ‘F’ if
a
is Fortran contiguous, ‘C’ otherwise. ‘K’ means match the layout ofa
as closely as possible. (Note that this function and :func:numpy.copy are very similar, but have different default values for their order= arguments.) Default is ‘C’.- data : array, optional
If supplied then use a view of
data
instead of the instance data. This allows copying the instance attributes and meta.- copy_data : bool, optional
Make a copy of the internal numpy array instead of using a reference. Default is True.
Returns: - col : Column or MaskedColumn
Copy of the current column (same type as original)
-
insert
(obj, values, axis=0)[source] [edit on github]¶ Insert values before the given indices in the column and return a new
Column
object.Parameters: - obj : int, slice or sequence of ints
Object that defines the index or indices before which
values
is inserted.- values : array_like
Value(s) to insert. If the type of
values
is different from that of quantity,values
is converted to the matching type.values
should be shaped so that it can be broadcast appropriately- axis : int, optional
Axis along which to insert
values
. Ifaxis
is None then the column array is flattened before insertion. Default is 0, which will insert a row.
Returns: - out :
Column
A copy of column with
values
andmask
inserted. Note that the insertion does not occur in-place: a new column is returned.
-
more
(max_lines=None, show_name=True, show_unit=False) [edit on github]¶ Interactively browse column with a paging interface.
Supported keys:
f, <space> : forward one page b : back one page r : refresh same page n : next row p : previous row < : go to beginning > : go to end q : quit browsing h : print this help
Parameters: - max_lines : int
Maximum number of lines in table output.
- show_name : bool
Include a header row for column names. Default is True.
- show_unit : bool
Include a header row for unit. Default is False.
-
pformat
(max_lines=None, show_name=True, show_unit=False, show_dtype=False, html=False) [edit on github]¶ Return a list of formatted string representation of column values.
If no value of
max_lines
is supplied then the height of the screen terminal is used to setmax_lines
. If the terminal height cannot be determined then the default will be determined using theastropy.conf.max_lines
configuration item. If a negative value ofmax_lines
is supplied then there is no line limit applied.Parameters: - max_lines : int
Maximum lines of output (header + data rows)
- show_name : bool
Include column name. Default is True.
- show_unit : bool
Include a header row for unit. Default is False.
- show_dtype : bool
Include column dtype. Default is False.
- html : bool
Format the output as an HTML table. Default is False.
Returns: - lines : list
List of lines with header and formatted column values
-
pprint
(max_lines=None, show_name=True, show_unit=False, show_dtype=False) [edit on github]¶ Print a formatted string representation of column values.
If no value of
max_lines
is supplied then the height of the screen terminal is used to setmax_lines
. If the terminal height cannot be determined then the default will be determined using theastropy.conf.max_lines
configuration item. If a negative value ofmax_lines
is supplied then there is no line limit applied.Parameters: - max_lines : int
Maximum number of values in output
- show_name : bool
Include column name. Default is True.
- show_unit : bool
Include a header row for unit. Default is False.
- show_dtype : bool
Include column dtype. Default is True.
-
to
(unit, equivalencies=[], **kwargs) [edit on github]¶ Converts this table column to a
Quantity
object with the requested units.Parameters: - unit :
Unit
or str The unit to convert to (i.e., a valid argument to the
astropy.units.Quantity.to()
method).- equivalencies : list of equivalence pairs, optional
Equivalencies to use for this conversion. See
astropy.units.Quantity.to()
for more details.
Returns: - quantity :
Quantity
A quantity object with the contents of this column in the units
unit
.
- unit :