Tables

TableHDU

class pyfits.core.TableHDU(data=None, header=None, name=None)

Bases: pyfits.core._TableBaseHDU

FITS ASCII table extension HDU class.

Parameters :  

data : array

data of the table

header : Header instance

header to be used for the HDU

name : str

the EXTNAME value

add_checksum(when=None, override_datasum=False)

Add the CHECKSUM and DATASUM cards to this HDU with the values set to the checksum calculated for the HDU and the data respectively. The addition of the DATASUM card may be overridden.

Parameters :  

when : str, optional

comment string for the cards; by default the comments will represent the time when the checksum was calculated

override_datasum : bool, optional

add the CHECKSUM card only

Notes

For testing purposes, first call add_datasum with a when argument, then call add_checksum with a when argument and override_datasum set to True. This will provide consistent comments for both cards and enable the generation of a CHECKSUM card with a consistent value.

add_datasum(when=None)

Add the DATASUM card to this HDU with the value set to the checksum calculated for the data.

Parameters :  

when : str, optional

Comment string for the card that by default represents the time when the checksum was calculated

Returns :  

checksum : int

The calculated datasum

Notes

For testing purposes, provide a when argument to enable the comment value in the card to remain consistent. This will enable the generation of a CHECKSUM card with a consistent value.

copy()

Make a copy of the table HDU, both header and data are copied.

filebytes()

Calculates and returns the number of bytes that this HDU will write to a file.

Parameters :  None : Returns :  Number of bytes :

fileinfo()

Returns a dictionary detailing information about the locations of this HDU within any associated file. The values are only valid after a read or write of the associated file with no intervening changes to the HDUList.

Parameters :  

None :

Returns :  

dictionary or None :

The dictionary details information about the locations of this HDU within an associated file. Returns None when the HDU is not associated with a file.

Dictionary contents:

Key	Value
file	File object associated with the HDU
filemode	Mode in which the file was opened (readonly, copyonwrite, update, append, ostream)
hdrLoc	Starting byte location of header in file
datLoc	Starting byte location of data block in file
datSpan	Data size including padding

get_coldefs()

Returns the table’s column definitions.

req_cards(keywd, pos, test, fix_value, option, errlist)

Check the existence, location, and value of a required Card.

TODO: Write about parameters

If pos = None, it can be anywhere. If the card does not exist, the new card will have the fix_value as its value when created. Also check the card’s value by using the test argument.

run_option(option='warn', err_text='', fix_text='Fixed.', fix='pass', fixable=1)

Execute the verification with selected option.

size()

Size (in bytes) of the data portion of the HDU.

update()

Update header keywords to reflect recent changes of columns.

update_ext_name(value, comment=None, before=None, after=None, savecomment=False)

Update the extension name associated with the HDU.

If the keyword already exists in the Header, it’s value and/or comment will be updated. If it does not exist, a new card will be created and it will be placed before or after the specified location. If no before or after is specified, it will be appended at the end.

Parameters :  

value : str

value to be used for the new extension name

comment : str, optional

to be used for updating, default=None.

before : str or int, optional

name of the keyword, or index of the Card before which the new card will be placed in the Header. The argument before takes precedence over after if both specified.

after : str or int, optional

name of the keyword, or index of the Card after which the new card will be placed in the Header.

savecomment : bool, optional

When True, preserve the current comment for an existing keyword. The argument savecomment takes precedence over comment if both specified. If comment is not specified then the current comment will automatically be preserved.

update_ext_version(value, comment=None, before=None, after=None, savecomment=False)

Update the extension version associated with the HDU.

If the keyword already exists in the Header, it’s value and/or comment will be updated. If it does not exist, a new card will be created and it will be placed before or after the specified location. If no before or after is specified, it will be appended at the end.

Parameters :  

value : str

value to be used for the new extension version

comment : str, optional

to be used for updating, default=None.

before : str or int, optional

name of the keyword, or index of the Card before which the new card will be placed in the Header. The argument before takes precedence over after if both specified.

after : str or int, optional

name of the keyword, or index of the Card after which the new card will be placed in the Header.

savecomment : bool, optional

When True, preserve the current comment for an existing keyword. The argument savecomment takes precedence over comment if both specified. If comment is not specified then the current comment will automatically be preserved.

verify(option='warn')

Verify all values in the instance.

Parameters :  

option : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". See Verification options for more info.

verify_checksum()

Verify that the value in the CHECKSUM keyword matches the value calculated for the current HDU CHECKSUM.

Returns :  

valid : int

• 0 - failure
• 1 - success
• 2 - no CHECKSUM keyword present

verify_datasum()

Verify that the value in the DATASUM keyword matches the value calculated for the DATASUM of the current HDU data.

Returns :  

valid : int

• 0 - failure
• 1 - success
• 2 - no DATASUM keyword present

writeto(name, output_verify='exception', clobber=False, classExtensions={}, checksum=False)

Write the HDU to a new file. This is a convenience method to provide a user easier output interface if only one HDU needs to be written to a file.

Parameters :  

name : file path, file object or file-like object

Output FITS file. If opened, must be opened for append (“ab+”)).

output_verify : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". See Verification options for more info.

clobber : bool

Overwrite the output file if exists, default = False.

classExtensions : dict

A dictionary that maps pyfits classes to extensions of those classes. When present in the dictionary, the extension class will be constructed in place of the pyfits class.

checksum : bool

When True, adds both DATASUM and CHECKSUM cards to the header of the HDU when written to the file.

BinTableHDU

class pyfits.core.BinTableHDU(data=None, header=None, name=None)

Bases: pyfits.core._TableBaseHDU

Binary table HDU class.

Parameters :  

data : array

data of the table

header : Header instance

header to be used for the HDU

name : str

the EXTNAME value

add_checksum(when=None, override_datasum=False)

Add the CHECKSUM and DATASUM cards to this HDU with the values set to the checksum calculated for the HDU and the data respectively. The addition of the DATASUM card may be overridden.

Parameters :  

when : str, optional

comment string for the cards; by default the comments will represent the time when the checksum was calculated

override_datasum : bool, optional

add the CHECKSUM card only

Notes

For testing purposes, first call add_datasum with a when argument, then call add_checksum with a when argument and override_datasum set to True. This will provide consistent comments for both cards and enable the generation of a CHECKSUM card with a consistent value.

add_datasum(when=None)

Add the DATASUM card to this HDU with the value set to the checksum calculated for the data.

Parameters :  

when : str, optional

Comment string for the card that by default represents the time when the checksum was calculated

Returns :  

checksum : int

The calculated datasum

Notes

For testing purposes, provide a when argument to enable the comment value in the card to remain consistent. This will enable the generation of a CHECKSUM card with a consistent value.

copy()

Make a copy of the table HDU, both header and data are copied.

filebytes()

Calculates and returns the number of bytes that this HDU will write to a file.

Parameters :  None : Returns :  Number of bytes :

fileinfo()

Returns a dictionary detailing information about the locations of this HDU within any associated file. The values are only valid after a read or write of the associated file with no intervening changes to the HDUList.

Parameters :  

None :

Returns :  

dictionary or None :

The dictionary details information about the locations of this HDU within an associated file. Returns None when the HDU is not associated with a file.

Dictionary contents:

Key	Value
file	File object associated with the HDU
filemode	Mode in which the file was opened (readonly, copyonwrite, update, append, ostream)
hdrLoc	Starting byte location of header in file
datLoc	Starting byte location of data block in file
datSpan	Data size including padding

get_coldefs()

Returns the table’s column definitions.

req_cards(keywd, pos, test, fix_value, option, errlist)

Check the existence, location, and value of a required Card.

TODO: Write about parameters

If pos = None, it can be anywhere. If the card does not exist, the new card will have the fix_value as its value when created. Also check the card’s value by using the test argument.

run_option(option='warn', err_text='', fix_text='Fixed.', fix='pass', fixable=1)

Execute the verification with selected option.

size()

Size (in bytes) of the data portion of the HDU.

tcreate(datafile, cdfile=None, hfile=None, replace=False)

Create a table from the input ASCII files. The input is from up to three separate files, one containing column definitions, one containing header parameters, and one containing column data. The column definition and header parameters files are not required. When absent the column definitions and/or header parameters are taken from the current values in this HDU.

Parameters :  

datafile : file path, file object or file-like object

Input data file containing the table data in ASCII format.

cdfile : file path, file object, file-like object, optional

Input column definition file containing the names, formats, display formats, physical units, multidimensional array dimensions, undefined values, scale factors, and offsets associated with the columns in the table. If None, the column definitions are taken from the current values in this object.

hfile : file path, file object, file-like object, optional

Input parameter definition file containing the header parameter definitions to be associated with the table. If None, the header parameter definitions are taken from the current values in this objects header.

replace : bool

When True, indicates that the entire header should be replaced with the contents of the ASCII file instead of just updating the current header.

Notes

The primary use for the tcreate method is to allow the input of ASCII data that was edited in a standard text editor of the table data and parameters. The tdump method can be used to create the initial ASCII files.

• datafile: Each line of the data file represents one row of table data. The data is output one column at a time in column order. If a column contains an array, each element of the column array in the current row is output before moving on to the next column. Each row ends with a new line.

  Integer data is output right-justified in a 21-character field followed by a blank. Floating point data is output right justified using ‘g’ format in a 21-character field with 15 digits of precision, followed by a blank. String data that does not contain whitespace is output left-justified in a field whose width matches the width specified in the TFORM header parameter for the column, followed by a blank. When the string data contains whitespace characters, the string is enclosed in quotation marks (""). For the last data element in a row, the trailing blank in the field is replaced by a new line character.

  For column data containing variable length arrays (‘P’ format), the array data is preceded by the string 'VLA_Length= ' and the integer length of the array for that row, left-justified in a 21-character field, followed by a blank.

  For column data representing a bit field (‘X’ format), each bit value in the field is output right-justified in a 21-character field as 1 (for true) or 0 (for false).

• cdfile: Each line of the column definitions file provides the definitions for one column in the table. The line is broken up into 8, sixteen-character fields. The first field provides the column name (TTYPEn). The second field provides the column format (TFORMn). The third field provides the display format (TDISPn). The fourth field provides the physical units (TUNITn). The fifth field provides the dimensions for a multidimensional array (TDIMn). The sixth field provides the value that signifies an undefined value (TNULLn). The seventh field provides the scale factor (TSCALn). The eighth field provides the offset value (TZEROn). A field value of "" is used to represent the case where no value is provided.

• hfile: Each line of the header parameters file provides the definition of a single HDU header card as represented by the card image.

tdump(datafile=None, cdfile=None, hfile=None, clobber=False)

Dump the table HDU to a file in ASCII format. The table may be dumped in three separate files, one containing column definitions, one containing header parameters, and one for table data.

Parameters :  

datafile : file path, file object or file-like object, optional

Output data file. The default is the root name of the fits file associated with this HDU appended with the extension .txt.

cdfile : file path, file object or file-like object, optional

Output column definitions file. The default is None, no column definitions output is produced.

hfile : file path, file object or file-like object, optional

Output header parameters file. The default is None, no header parameters output is produced.

clobber : bool

Overwrite the output files if they exist.

Notes

The primary use for the tdump method is to allow editing in a standard text editor of the table data and parameters. The tcreate method can be used to reassemble the table from the three ASCII files.

• datafile: Each line of the data file represents one row of table data. The data is output one column at a time in column order. If a column contains an array, each element of the column array in the current row is output before moving on to the next column. Each row ends with a new line.

  Integer data is output right-justified in a 21-character field followed by a blank. Floating point data is output right justified using ‘g’ format in a 21-character field with 15 digits of precision, followed by a blank. String data that does not contain whitespace is output left-justified in a field whose width matches the width specified in the TFORM header parameter for the column, followed by a blank. When the string data contains whitespace characters, the string is enclosed in quotation marks (""). For the last data element in a row, the trailing blank in the field is replaced by a new line character.

  For column data containing variable length arrays (‘P’ format), the array data is preceded by the string 'VLA_Length= ' and the integer length of the array for that row, left-justified in a 21-character field, followed by a blank.

  For column data representing a bit field (‘X’ format), each bit value in the field is output right-justified in a 21-character field as 1 (for true) or 0 (for false).

• cdfile: Each line of the column definitions file provides the definitions for one column in the table. The line is broken up into 8, sixteen-character fields. The first field provides the column name (TTYPEn). The second field provides the column format (TFORMn). The third field provides the display format (TDISPn). The fourth field provides the physical units (TUNITn). The fifth field provides the dimensions for a multidimensional array (TDIMn). The sixth field provides the value that signifies an undefined value (TNULLn). The seventh field provides the scale factor (TSCALn). The eighth field provides the offset value (TZEROn). A field value of "" is used to represent the case where no value is provided.

• hfile: Each line of the header parameters file provides the definition of a single HDU header card as represented by the card image.

update()

Update header keywords to reflect recent changes of columns.

update_ext_name(value, comment=None, before=None, after=None, savecomment=False)

Update the extension name associated with the HDU.

If the keyword already exists in the Header, it’s value and/or comment will be updated. If it does not exist, a new card will be created and it will be placed before or after the specified location. If no before or after is specified, it will be appended at the end.

Parameters :  

value : str

value to be used for the new extension name

comment : str, optional

to be used for updating, default=None.

before : str or int, optional

name of the keyword, or index of the Card before which the new card will be placed in the Header. The argument before takes precedence over after if both specified.

after : str or int, optional

name of the keyword, or index of the Card after which the new card will be placed in the Header.

savecomment : bool, optional

When True, preserve the current comment for an existing keyword. The argument savecomment takes precedence over comment if both specified. If comment is not specified then the current comment will automatically be preserved.

update_ext_version(value, comment=None, before=None, after=None, savecomment=False)

Update the extension version associated with the HDU.

If the keyword already exists in the Header, it’s value and/or comment will be updated. If it does not exist, a new card will be created and it will be placed before or after the specified location. If no before or after is specified, it will be appended at the end.

Parameters :  

value : str

value to be used for the new extension version

comment : str, optional

to be used for updating, default=None.

before : str or int, optional

name of the keyword, or index of the Card before which the new card will be placed in the Header. The argument before takes precedence over after if both specified.

after : str or int, optional

name of the keyword, or index of the Card after which the new card will be placed in the Header.

savecomment : bool, optional

When True, preserve the current comment for an existing keyword. The argument savecomment takes precedence over comment if both specified. If comment is not specified then the current comment will automatically be preserved.

verify(option='warn')

Verify all values in the instance.

Parameters :  

option : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". See Verification options for more info.

verify_checksum()

Verify that the value in the CHECKSUM keyword matches the value calculated for the current HDU CHECKSUM.

Returns :  

valid : int

• 0 - failure
• 1 - success
• 2 - no CHECKSUM keyword present

verify_datasum()

Verify that the value in the DATASUM keyword matches the value calculated for the DATASUM of the current HDU data.

Returns :  

valid : int

• 0 - failure
• 1 - success
• 2 - no DATASUM keyword present

writeto(name, output_verify='exception', clobber=False, classExtensions={}, checksum=False)

Write the HDU to a new file. This is a convenience method to provide a user easier output interface if only one HDU needs to be written to a file.

Parameters :  

name : file path, file object or file-like object

Output FITS file. If opened, must be opened for append (“ab+”)).

output_verify : str

Output verification option. Must be one of "fix", "silentfix", "ignore", "warn", or "exception". See Verification options for more info.

clobber : bool

Overwrite the output file if exists, default = False.

classExtensions : dict

A dictionary that maps pyfits classes to extensions of those classes. When present in the dictionary, the extension class will be constructed in place of the pyfits class.

checksum : bool

When True, adds both DATASUM and CHECKSUM cards to the header of the HDU when written to the file.

Column

class pyfits.core.Column(name=None, format=None, unit=None, null=None, bscale=None, bzero=None, disp=None, start=None, dim=None, array=None)

Class which contains the definition of one column, e.g. ttype, tform, etc. and the array containing values for the column. Does not support theap yet.

Construct a Column by specifying attributes. All attributes except format can be optional.

Parameters :  

name : str, optional

column name, corresponding to TTYPE keyword

format : str, optional

column format, corresponding to TFORM keyword

unit : str, optional

column unit, corresponding to TUNIT keyword

null : str, optional

null value, corresponding to TNULL keyword

bscale : int-like, optional

bscale value, corresponding to TSCAL keyword

bzero : int-like, optional

bzero value, corresponding to TZERO keyword

disp : str, optional

display format, corresponding to TDISP keyword

start : int, optional

column starting position (ASCII table only), corresponding to TBCOL keyword

dim : str, optional

column dimension corresponding to TDIM keyword

copy()

Return a copy of this Column.

ColDefs

class pyfits.core.ColDefs(input, tbtype='BinTableHDU')

Bases: object

Column definitions class.

It has attributes corresponding to the Column attributes (e.g. ColDefs has the attribute names while Column has name). Each attribute in ColDefs is a list of corresponding attribute values from all Column objects.

Parameters :  

input : sequence of Column objects

an (table) HDU

tbtype : str, optional

which table HDU, "BinTableHDU" (default) or "TableHDU" (text table).

add_col(column)

Append one Column to the column definition.

Warning

New in pyfits 2.3: This function appends the new column to the ColDefs object in place. Prior to pyfits 2.3, this function returned a new ColDefs with the new column at the end.

change_attrib(col_name, attrib, new_value)

Change an attribute (in the commonName list) of a Column.

col_name : str or int

The column name or index to change

attrib : str

The attribute name

value : object

The new value for the attribute

change_name(col_name, new_name)

Change a Column‘s name.

col_name : str

The current name of the column

new_name : str

The new name of the column

change_unit(col_name, new_unit)

Change a Column‘s unit.

col_name : str or int

The column name or index

new_unit : str

The new unit for the column

del_col(col_name)

Delete (the definition of) one Column.

col_name : str or int

The column’s name or index

info(attrib='all')

Get attribute(s) information of the column definition.

Parameters :  

attrib : str

Can be one or more of the attributes listed in _commonNames. The default is "all" which will print out all attributes. It forgives plurals and blanks. If there are two or more attribute names, they must be separated by comma(s).

Notes

This function doesn’t return anything, it just prints to stdout.

FITS_record

class pyfits.core.FITS_record(input, row=0, startColumn=0, endColumn=0)

Bases: object

FITS record class.

FITS_record is used to access records of the FITS_rec object. This will allow us to deal with scaled columns. The FITS_record class expects a FITS_rec object as input.

Parameters :  

input : array

The array to wrap.

row : int, optional

The starting logical row of the array.

startColumn : int, optional

The starting column in the row associated with this object. Used for subsetting the columns of the FITS_rec object.

endColumn : int, optional

The ending column in the row associated with this object. Used for subsetting the columns of the FITS_rec object.

field(fieldName)

Get the field data of the record.

setfield(fieldName, value)

Set the field data of the record.

FITS_rec

class pyfits.core.FITS_rec

Bases: pyfits.rec.recarray

FITS record array class.

FITS_rec is the data part of a table HDU’s data part. This is a layer over the recarray, so we can deal with scaled columns.

It inherits all of the standard methods from numpy.ndarray.

field(key)

A view of a Column‘s data as an array.

GroupData

class pyfits.core.GroupData

Bases: pyfits.core.FITS_rec

Random groups data object.

Allows structured access to FITS Group data in a manner analogous to tables.

par(parName)

Get the group parameter values.

Free functions

new_table

pyfits.core.new_table(input, header=None, nrows=0, fill=False, tbtype='BinTableHDU')

Create a new table from the input column definitions.

Parameters :  

input : sequence of Column or ColDefs objects

The data to create a table from.

header : Header instance

Header to be used to populate the non-required keywords.

nrows : int

Number of rows in the new table.

fill : bool

If True, will fill all cells with zeros or blanks. If False, copy the data from input, undefined cells will still be filled with zeros/blanks.

tbtype : str

Table type to be created (“BinTableHDU” or “TableHDU”).

tdump

pyfits.core.tdump(fitsFile, datafile=None, cdfile=None, hfile=None, ext=1, clobber=False, classExtensions={})

Dump a table HDU to a file in ASCII format. The table may be dumped in three separate files, one containing column definitions, one containing header parameters, and one for table data.

Parameters :  

fitsFile : file path, file object or file-like object

Input fits file.

datafile : file path, file object or file-like object, optional

Output data file. The default is the root name of the input fits file appended with an underscore, followed by the extension number (ext), followed by the extension .txt.

cdfile : file path, file object or file-like object, optional

Output column definitions file. The default is None, no column definitions output is produced.

hfile : file path, file object or file-like object, optional

Output header parameters file. The default is None, no header parameters output is produced.

ext : int

The number of the extension containing the table HDU to be dumped.

clobber : bool

Overwrite the output files if they exist.

classExtensions : dict

A dictionary that maps pyfits classes to extensions of those classes. When present in the dictionary, the extension class will be constructed in place of the pyfits class.

Notes

The primary use for the tdump function is to allow editing in a standard text editor of the table data and parameters. The tcreate function can be used to reassemble the table from the three ASCII files.

• datafile: Each line of the data file represents one row of table data. The data is output one column at a time in column order. If a column contains an array, each element of the column array in the current row is output before moving on to the next column. Each row ends with a new line.

  Integer data is output right-justified in a 21-character field followed by a blank. Floating point data is output right justified using ‘g’ format in a 21-character field with 15 digits of precision, followed by a blank. String data that does not contain whitespace is output left-justified in a field whose width matches the width specified in the TFORM header parameter for the column, followed by a blank. When the string data contains whitespace characters, the string is enclosed in quotation marks (""). For the last data element in a row, the trailing blank in the field is replaced by a new line character.

  For column data containing variable length arrays (‘P’ format), the array data is preceded by the string 'VLA_Length= ' and the integer length of the array for that row, left-justified in a 21-character field, followed by a blank.

  For column data representing a bit field (‘X’ format), each bit value in the field is output right-justified in a 21-character field as 1 (for true) or 0 (for false).

• cdfile: Each line of the column definitions file provides the definitions for one column in the table. The line is broken up into 8, sixteen-character fields. The first field provides the column name (TTYPEn). The second field provides the column format (TFORMn). The third field provides the display format (TDISPn). The fourth field provides the physical units (TUNITn). The fifth field provides the dimensions for a multidimensional array (TDIMn). The sixth field provides the value that signifies an undefined value (TNULLn). The seventh field provides the scale factor (TSCALn). The eighth field provides the offset value (TZEROn). A field value of "" is used to represent the case where no value is provided.

• hfile: Each line of the header parameters file provides the definition of a single HDU header card as represented by the card image.

tcreate

pyfits.core.tcreate(datafile, cdfile, hfile=None)

Create a table from the input ASCII files. The input is from up to three separate files, one containing column definitions, one containing header parameters, and one containing column data. The header parameters file is not required. When the header parameters file is absent a minimal header is constructed.

Parameters :  

datafile : file path, file object or file-like object

Input data file containing the table data in ASCII format.

cdfile : file path, file object or file-like object

Input column definition file containing the names, formats, display formats, physical units, multidimensional array dimensions, undefined values, scale factors, and offsets associated with the columns in the table.

hfile : file path, file object or file-like object, optional

Input parameter definition file containing the header parameter definitions to be associated with the table. If None, a minimal header is constructed.

Notes

The primary use for the tcreate function is to allow the input of ASCII data that was edited in a standard text editor of the table data and parameters. The tdump function can be used to create the initial ASCII files.

• datafile: Each line of the data file represents one row of table data. The data is output one column at a time in column order. If a column contains an array, each element of the column array in the current row is output before moving on to the next column. Each row ends with a new line.

  Integer data is output right-justified in a 21-character field followed by a blank. Floating point data is output right justified using ‘g’ format in a 21-character field with 15 digits of precision, followed by a blank. String data that does not contain whitespace is output left-justified in a field whose width matches the width specified in the TFORM header parameter for the column, followed by a blank. When the string data contains whitespace characters, the string is enclosed in quotation marks (""). For the last data element in a row, the trailing blank in the field is replaced by a new line character.

  For column data containing variable length arrays (‘P’ format), the array data is preceded by the string 'VLA_Length= ' and the integer length of the array for that row, left-justified in a 21-character field, followed by a blank.

  For column data representing a bit field (‘X’ format), each bit value in the field is output right-justified in a 21-character field as 1 (for true) or 0 (for false).

• cdfile: Each line of the column definitions file provides the definitions for one column in the table. The line is broken up into 8, sixteen-character fields. The first field provides the column name (TTYPEn). The second field provides the column format (TFORMn). The third field provides the display format (TDISPn). The fourth field provides the physical units (TUNITn). The fifth field provides the dimensions for a multidimensional array (TDIMn). The sixth field provides the value that signifies an undefined value (TNULLn). The seventh field provides the scale factor (TSCALn). The eighth field provides the offset value (TZEROn). A field value of "" is used to represent the case where no value is provided.

• hfile: Each line of the header parameters file provides the definition of a single HDU header card as represented by the card image.