Class Variable
object --+
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Variable
A netCDF Variable is used to read and write netCDF data. They
are analagous to numpy array objects.
Variable(dataset, name, datatype, dimensions=(), zlib=True,
complevel=6, shuffle=True, fletcher32=False, chunking='seq',
least_significant_digit=None, fill_value=None)
Variable instances should be created using the
createVariable
method of a Dataset
instance, not using this class directly.
Parameters:
dataset
- Dataset
instance to associate with variable.
name
- Name of the variable.
datatype
- Variable data
type, one of 'f4'
(32-bit floating point), 'f8'
(64-bit floating point), 'i4'
(32-bit signed integer),
'i2'
(16-bit signed integer), 'i4'
(8-bit
singed integer), 'i1'
(8-bit signed integer) or
'S1'
(single-character string). The old single character
Numeric typecodes ('f','d','c','i','h','b'
) are also
accepted
Keywords:
dimensions
- a tuple containing the variable's
dimension names (defined previously with createDimension
).
Default is an empty tuple which means the variable is a scalar (and
therefore has no dimensions).
zlib
- if True
(default), data
assigned to the Variable instance is compressed on disk.
complevel
- the level of zlib compression to use
(1 is the fastest, but poorest compression, 9 is the slowest but best
compression). Default 6.
shuffle
- if True
(default), the HDF5
shuffle filter is applied to improve compression.
fletcher32
- if True
(default
False
), the Fletcher32 checksum algorithm is used for error
detection.
chunking
- Chunking is required in any dataset
with one or more unlimited dimension in HDF5. NetCDF-4 supports setting
the chunking algorithm at variable creation. If chunking =
'seq'
(default) chunk sizes are set to favor sequential access.
Setting chunking = 'sub'
will cause chunk sizes to be set to
favor subsetting equally in any dimension.
least_significant_digit
- If specified, variable
data will be truncated (quantized). This produces 'lossy', but
significantly more efficient compression. For example, if
least_significant_digit=1
, data will be quantized using
around(scale*data)/scale, where scale = 2**bits, and bits is determined
so that a precision of 0.1 is retained (in this case bits=4). Default is
None
, or no quantization.
fill_value
- If specified, the default netCDF
_FillValue
(the value that the variable gets filled with
before any data is written to it) is replaced with this value. If
fill_value is set to False
, then the variable is not
pre-filled.
Returns:
a Variable instance. All further operations on the netCDF
Variable are accomplised via Variable
instance methods.
A list of attribute names corresponding to netCDF attributes defined
for the variable can be obtained with the ncattrs()
method.
These attributes can be created by assigning to an attribute of the Variable
instance. A dictionary containing all the netCDF attribute name/value
pairs is provided by the __dict__
attribute of a Variable
instance.
The instance variables dimensions, dtype, shape
and
least_significant_digits
are read-only (and should not be
modified by the user).
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__delattr__(...)
x.__delattr__('name') <==> del x.name
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__delitem__(x,
y)
del x[y]
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__getattribute__(...)
x.__getattribute__('name') <==> x.name
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__getitem__(x,
y)
x[y]
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__init__(...)
x.__init__(...) initializes x; see x.__class__.__doc__ for
signature
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__new__(T,
S,
...)
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__setattr__(...)
x.__setattr__('name', value) <==> x.name = value
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__setitem__(x,
i,
y)
x[i]=y
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_get(...)
Private method to retrieve data from a netCDF variable
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_getDimensions(...)
Private method to get variables's dimension names
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_put(...)
Private method to put data into a netCDF variable
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_shape(...)
Private method to find current sizes of all variable
dimensions
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assignValue(...)
assign a value to a scalar variable.
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getValue(...)
get the value of a scalar variable.
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ncattrs(...)
return names of netCDF attribute for this Variable
in a list
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typecode(...)
return dtype attribute, provided for compatibility with
Scientific.IO.NetCDF
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Inherited from object :
__hash__ ,
__reduce__ ,
__reduce_ex__ ,
__repr__ ,
__str__
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_dsetid = <member '_dsetid' of 'netCDF4_classic.Variable' obje...
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_varid = <member '_varid' of 'netCDF4_classic.Variable' objects>
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dimensions
A tuple containing the names of the dimensions associated with
this variable.
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dtype = <member 'dtype' of 'netCDF4_classic.Variable' objects>
A description of the variable's data type
('i4','f8','S1' , etc).
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least_significant_digit
Describes the power of ten of the smallest decimal place in the
data the contains a reliable value.
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shape
a tuple describing the current size of all the variable's
dimensions.
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Inherited from object :
__class__
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x.__delattr__('name') <==> del x.name
-
- Overrides:
object.__delattr__
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__delitem__(x,
y)
(Index deletion operator)
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del x[y]
-
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x.__getattribute__('name') <==> x.name
-
- Overrides:
object.__getattribute__
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__getitem__(x,
y)
(Indexing operator)
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x[y]
-
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__init__(...)
(Constructor)
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x.__init__(...) initializes x; see x.__class__.__doc__ for
signature
-
- Overrides:
object.__init__
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-
- Returns:
a new object with type S, a subtype of T
- Overrides:
object.__new__
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x.__setattr__('name', value) <==> x.name = value
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- Overrides:
object.__setattr__
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__setitem__(x,
i,
y)
(Index assignment operator)
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x[i]=y
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Private method to retrieve data from a netCDF variable
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Private method to get variables's dimension names
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Private method to put data into a netCDF variable
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Private method to find current sizes of all variable dimensions
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assign a value to a scalar variable. Provided for compatibility with
Scientific.IO.NetCDF, can also be done by assigning to a slice ([:]).
assignValue(val)
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get the value of a scalar variable. Provided for compatibility with
Scientific.IO.NetCDF, can also be done by slicing ([:]).
getValue()
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return names of netCDF attribute for this Variable in a
list
ncattrs()
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return dtype attribute, provided for compatibility with
Scientific.IO.NetCDF
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_dsetid
None
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- Value:
<member '_dsetid' of 'netCDF4_classic.Variable' objects>
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_varid
None
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- Value:
<member '_varid' of 'netCDF4_classic.Variable' objects>
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dimensions
A tuple containing the names of the dimensions associated with this
variable.
-
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dtype
A description of the variable's data type
('i4','f8','S1' , etc).
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- Value:
<member 'dtype' of 'netCDF4_classic.Variable' objects>
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least_significant_digit
Describes the power of ten of the smallest decimal place in the data
the contains a reliable value. Data is truncated to this decimal place
when it is assigned to the Variable instance. If None , the data is not
truncated.
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shape
a tuple describing the current size of all the variable's
dimensions.
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