cf.of_fraction¶

cf.of_fraction(*arg)[source]

The amount of concurrently open files above which files containing data arrays may be automatically closed.

The amount is expressed as a fraction of the maximum possible number of concurrently open files.

Note that closed files will be automatically reopened if subsequently needed by a variable to access its data array.

Parameters
arg: float or Constant, optional

The new fraction (between 0.0 and 1.0). The default is to not change the current behaviour.

Returns
Constant

The value prior to the change, or the current value if no new value was specified.

Examples:

>>> cf.of_fraction()
0.5
>>> old = cf.of_fraction(0.33)
>>> cf.of_fraction(old)
0.33
>>> cf.of_fraction()
0.5


The fraction may be translated to an actual number of files as follows:

>>> old = cf.of_fraction(0.75)
>>> import resource
>>> max_open_files = resource.getrlimit(resource.RLIMIT_NOFILE)[0]
>>> threshold = int(max_open_files * cf.of_fraction())
>>> max_open_files, threshold
(1024, 768)