3.2.1.0 table.create

NRAO Home > CASA > CASA Toolkit Reference Manual

table.create - Function

3.2.1 create a new table

Description

Create a new CASA Table.

Most of the time you just need to specify the table’s name and a description of its format.

A table can be shared by multiple processes by using the appropriate locking options. The possible options are:
- auto: let the system take care of locking. At regular time intervals these autolocks are released to give other processes the opportunity to access the table.
- autonoread: as auto, but no read locking is needed. This must be used with care, because it means that reading can be done while the table tool is not synchronized with the table file (as is normally done when a lock is acquired). The function resync can be used to explicitly synchronize the table tool
- user: the user takes care by explicit calls to lock and unlock
- usernoread: as user and the no readlocking behaviour of autonoread.
- permanent: use a permanent lock; the constructor fails when the table is already in use in another process
- permanentwait: as above, but wait until the other process releases its lock
- default: this is the default option. If the given table is already open, the locking option in use is not changed. Otherwise it reverts to auto.
When auto locking is used, it is possible to give a record containing the fields option, interval, and/or maxwait. In this way advanced users have full control over the locking options. In practice this is hardly ever needed.

Arguments


Inputs
tablename
	allowed:	string
	Default:
tabledesc	description of the table’s format
	allowed:	record
	Default:
lockoptions	locking to be used
	allowed:	record
	Default:	default
endianformat
	allowed:	string
	Default:
memtype
	allowed:	string
	Default:
nrow
	allowed:	int
	Default:	0
dminfo	Data Manager information
	allowed:	record
	Default:

Returns
bool

Example

  # First let’s get sample descriptions of a table and its data managers.
  import os, shutil

  def get_tabledesc_and_dminfo(tabname="3C273XC1.MS"):
      made_copy = False

      # Fetch new table if tabname not present
      if not os.path.isdir(tabname):
          # Get path to CASA root directory by stripping name from ’$CASAPATH’
          pathname = os.environ.get("CASAPATH").split()[0]

          # There should be some data here
          fitsdata = pathname + "/data/demo/3C273XC1.fits"
          tabname = "3C273XC1.MS"

          ms.fromfits(tabname, fitsdata)
          ms.close()
          made_copy = True

      tb.open(tabname)
      tabdesc = tb.getdesc()
      dminfo  = tb.getdminfo()
      print tabname, "has", tb.nrows(), "rows."
      tb.close()

      # Clean up
      if made_copy:
          shutil.rmtree(tabname)

      return tabdesc, dminfo

  tabdesc, dmi = get_tabledesc_and_dminfo()
  tabdesc  # prints tabdesc
  dmi      # prints dmi

  # You could alter tabdesc and/or dmi at this point.

  # Unnecessary, but just to show there is nothing up my sleeve...
  tb.close()

  tb.create("myempty.ms", tabdesc, dminfo=dmi)
  tb.nrows()     # 0L
  tb.addrows(5)  # Add the rows _before_ filling the columns.
  tb.putcol(’ARRAY_ID’, numpy.array([0 for i in range(5)]))
  tb.putcol(’ANTENNA1’, numpy.array(range(5)))
  tb.putcol(’ANTENNA2’, numpy.array(range(1,6)))
  tb.browse()    # Still mostly, but not completely, empty.
  tb.close()

This creates a CASA table using a description of a table and its data managers from an existing MS.

__________________________________________________________________

[next] [prev] [prev-tail] [front] [up]

More information about CASA may be found at the CASA web page

This code is available under the terms of the GNU General Public Lincense