nctoolkit let’s you set global settings using options.
The most important and recommended to update is to set evaluation to lazy. This can be done as follows:
nc.options(lazy = True)
This means that commands will only be evaluated when either request them to be or they need to be.
For example, in the code below the 3 specified commands will only be
calculated after it is told to
run. This cuts down on IO, and can
result in significant improvements in run time. At present lazy defaults
to False, but this may change in a future release of nctoolkit.
nc.options(lazy = True) data.tmean() data.crop(lat = [0,90]) data.spatial_mean() data.run()
If you are working with ensembles, you may want to change the number of cores used for processing multiple files. For example, you can process multiple files in parallel using 6 cores as follows. By default cores = 1. Most methods can run in parallel when working with multi-file datasets.
nc.options(cores = 6)
By default nctoolkit uses the OS’s temporary directories when it needs to create temporary files. In most cases this is optimal. Most of the time reading and writing to temporary folders is faster. However, in some cases this may not be a good idea because you may not have enough space in the temporary folder. In this case you can change the directory used for saving temporary files as follows:
nc.options(temp_dir = "/foo")
Setting global settings using a configuration file¶
You may want to set some global settings either permanently or on a project level. You can do this by setting up a configruation file. This should be a plain text file called .nctoolkitrc or nctoolkitrc. It should be placed in one of two locations: your working directory or your home directory. When nctoolkit is imported, it will look first in your working directory and then in your home directory for a file called .nctoolkitrc or nctoolkitrc. It will then use the first it finds to change the global settings from the defaults.
The structure of this file is straightforward. For example, if you wanted to set evaluation to lazy and the number of cores used for processing multi-file datasets, you would the following in your configuration file:
lazy : True
cores : 6
The files roughly follow Python dictionary syntax, with the setting and value separate by :. Note that unless the setting is specified in the file, the defaults will be used. If you do not provide a configuration file, nctoolkit will use the default settings.