yanny¶
- class pydl.pydlutils.yanny.yanny(filename=None, raw=False)[source]¶
Bases:
OrderedDict
An object interface to a yanny file.
Create a yanny object using a yanny file,
filename
. If the file exists, it is read, & the dict structure of the object will be basically the same as that returned byread_yanny()
in the efftickle package.If the file does not exist, or if no filename is given, a blank structure is returned. Other methods allow for subsequent writing to the file.
- Parameters:
- Attributes:
- raw
bool
If
True
, data in a yanny file will not be converted into astropyTable
objects, but will instead be retained as raw Python lists.- filename
str
The name of a yanny parameter file. If a file-like object was used to initialize the object, this will have the value ‘in_memory.par’.
- _symbols
dict
A dictionary containing the metadata describing the tables.
- _contents
str
The complete contents of a yanny parameter file.
- _struct_type_caches
dict
A dictionary of dictionaries, one dictionary for every structure definition in a yanny parameter file. Contains the types of each column
- _struct_isarray_caches
dict
A dictionary of dictionaries, one dictionary for every structure definition in a yanny parameter file. Contains a boolean value for every column.
- _enum_cache
dict
Initially
None
, this attribute is initialized the first time theisenum()
method is called. The keyword is the name of the enum type, the value is a list of the possible values of that type.
- raw
Create a yanny object using a yanny file.
Methods Summary
append
(datatable)Appends data to an existing FTCL/yanny file.
array_length
(structure, variable)Returns the length of an array type or 1 if the variable is not an array.
basetype
(structure, variable)Returns the bare type of a variable, stripping off any array information.
char_length
(structure, variable)Returns the length of a character field.
columns
(table)Returns an ordered list of column names associated with a particular table.
convert
(structure, variable, value)Converts value into the appropriate (Python) type.
dtype
(structure)Returns a NumPy dtype object suitable for describing a table as a record array.
dtype_to_struct
(dt[, structname, enums])Convert a NumPy dtype object describing a record array to a typedef struct statement.
get_token
(string)Removes the first 'word' from string.
isarray
(structure, variable)Returns
True
if the variable is an array type.isenum
(structure, variable)Returns true if a variable is an enum type.
list_of_dicts
(table)Construct a list of dictionaries.
Returns a new dictionary of keyword/value pairs.
pairs
()Returns a list of keys to keyword/value pairs.
protect
(x)Used to appropriately quote string that might contain whitespace.
row
(table, index)Returns a list containing a single row from a specified table in column order.
size
(table)Returns the number of rows in a table.
tables
()Returns a list of all the defined structures.
trailing_comment
(line)Identify a trailing comment and strip it.
type
(structure, variable)Returns the type of a variable defined in a structure.
write
([newfile, comments])Write a yanny object to a file.
Methods Documentation
- append(datatable)[source]¶
Appends data to an existing FTCL/yanny file.
Tries as much as possible to preserve the ordering & format of the original file. The datatable should adhere to the format of the yanny object, but it is not necessary to reproduce the ‘symbols’ dictionary. It will not try to append data to a file that does not exist. If the append is successful, the data in the object will be updated.
- Parameters:
- datatable
dict
The data to append.
- datatable
- array_length(structure, variable)[source]¶
Returns the length of an array type or 1 if the variable is not an array.
For character types, this is the length of a two-dimensional array, e.g.,
char[5][20]
has length 5.
- basetype(structure, variable)[source]¶
Returns the bare type of a variable, stripping off any array information.
- char_length(structure, variable)[source]¶
Returns the length of a character field.
e.g.
char[5][20]
is an array of 5 strings of length 20. ReturnsNone
if the variable is not a character type. If the length is not specified, i.e.char[]
, it returns the length of the largest string.
- columns(table)[source]¶
Returns an ordered list of column names associated with a particular table.
The order is the same order as they are defined in the yanny file.
- convert(structure, variable, value)[source]¶
Converts value into the appropriate (Python) type.
short
&int
are converted to Pythonint
.long
is converted to Pythonlong
.float
&double
are converted to Pythonfloat
.Other types are not altered.
There may be further conversions into NumPy types, but this is the first stage.
- dtype(structure)[source]¶
Returns a NumPy dtype object suitable for describing a table as a record array.
Treats enums as string, which is what the IDL reader does.
- Parameters:
- structure
str
The name of the structure.
- structure
- Returns:
numpy.dtype
A dtype object suitable for describing the yanny structure as a record array.
- static dtype_to_struct(dt, structname='mystruct', enums=None)[source]¶
Convert a NumPy dtype object describing a record array to a typedef struct statement.
The second argument is the name of the structure. If any of the columns are enum types, enums must be a dictionary with the keys the column names, and the values are a tuple containing the name of the enum type as the first item and a tuple or list of possible values as the second item.
- Parameters:
- dt
numpy.dtype
The dtype of a NumPy record array.
- structname
str
, optional The name to give the structure in the yanny file. Defaults to ‘MYSTRUCT’.
- enums
dict
, optional A dictionary containing enum information. See details above.
- dt
- Returns:
dict
A dictionary suitable for setting the ‘symbols’ dictionary of a new yanny object.
- static get_token(string)[source]¶
Removes the first ‘word’ from string.
If the ‘word’ is enclosed in double quotes, it returns the contents of the double quotes. If the ‘word’ is enclosed in braces, it returns the contents of the braces, but does not attempt to split the array. If the ‘word’ is the last word of the string, remainder is set equal to the empty string. This is basically a wrapper on some convenient regular expressions.
- Parameters:
- string
str
A string containing words.
- string
- Returns:
tuple
A tuple containing the first word and the remainder of the string.
Examples
>>> from pydl.pydlutils.yanny import yanny >>> yanny.get_token("The quick brown fox") ('The', 'quick brown fox')
- isarray(structure, variable)[source]¶
Returns
True
if the variable is an array type.For character types, this means a two-dimensional array, e.g.:
char[5][20]
.
- list_of_dicts(table)[source]¶
Construct a list of dictionaries.
Takes a table from the yanny object and constructs a list object containing one row per entry. Each item in the list is a dictionary keyed by the struct value names.
If the yanny object instance is set up for NumPy record arrays, then the same functionality can be obtained with:
foo = par['TABLE'][0]['column']
- new_dict_from_pairs()[source]¶
Returns a new dictionary of keyword/value pairs.
The new dictionary (i.e., not a yanny object) contains the keys that
pairs()
returns. There are two reasons this is convenient:the key ‘symbols’ that is part of the yanny object will not be present
a simple yanny file can be read with no further processing
- Returns:
OrderedDict
A dictionary of the keyword-value pairs that remembers the order in which they were defined in the file.
Examples
Read a yanny file and return only the pairs:
>>> from os.path import dirname >>> from pydl.pydlutils.yanny import yanny >>> y = yanny(dirname(__file__)+'/tests/t/test.par') >>> new_dict = y.new_dict_from_pairs() >>> new_dict['mjd'] '54579' >>> new_dict['alpha'] 'beta gamma delta'
added: Demitri Muna, NYU 2009-04-28
- pairs()[source]¶
Returns a list of keys to keyword/value pairs.
Equivalent to doing
self.keys()
, but with all the data tables & other control structures stripped out.
- static protect(x)[source]¶
Used to appropriately quote string that might contain whitespace.
This method is mostly for internal use by the yanny object.
Examples
>>> from pydl.pydlutils.yanny import yanny >>> yanny.protect('This string contains whitespace.') '"This string contains whitespace."' >>> yanny.protect('This string contains a #hashtag.') '"This string contains a #hashtag."'
- row(table, index)[source]¶
Returns a list containing a single row from a specified table in column order.
If index is out of range, it returns an empty list.
If the yanny object instance is set up for NumPy record arrays, then a single row can be obtained with:
row0 = par['TABLE'][0]
- tables()[source]¶
Returns a list of all the defined structures.
This is just the list of keys of the object with the ‘internal’ keys removed.
- static trailing_comment(line)[source]¶
Identify a trailing comment and strip it.
This routine works on the theory that a properly quoted comment mark will be surrounted by an odd number of double quotes, & we can skip to searching for the last one in the line.
- Parameters:
- line
str
A line from a yanny file potentially containing trailing comments.
- line
- Returns:
str
The line with any trailing comment and any residual white space trimmed off.
Notes
This may fail in certain pathological cases, for example if a real trailing comment contains a single double-quote:
# a 'pathological" trailing comment
or if someone is over-enthusiastically commenting:
# # # # # I like # characters.
Examples
>>> from pydl.pydlutils.yanny import yanny >>> yanny.trailing_comment('mystruct 1234 "#hashtag" # a comment.') 'mystruct 1234 "#hashtag"' >>> yanny.trailing_comment('mystruct 1234 "#hashtag" # a "comment".') 'mystruct 1234 "#hashtag"'
- type(structure, variable)[source]¶
Returns the type of a variable defined in a structure.
Returns
None
if the structure or the variable is undefined.
- write(newfile=None, comments=None)[source]¶
Write a yanny object to a file.
This assumes that the filename used to create the object was not that of a pre-existing file. If a file of the same name is detected, this method will not attempt to overwrite it, but will print a warning. This also assumes that the special ‘symbols’ key has been properly created. This will not necessarily make the file very human-readable, especially if the data lines are long. If the name of a new file is given, it will write to the new file (assuming it doesn’t exist). If the writing is successful, the data in the object will be updated.
- Parameters:
- newfile
str
, optional The name of the file to write.
- comments
str
orlist
ofstr
, optional Comments that will be placed at the head of the file. If a single string is passed, it will be written out verbatim, although a ‘#’ character will be added if it does not already have one. If a list of strings is passed, comment characters will be added and the strings will be joined together.
- newfile