Move `data_dir` definition

[tritemio]

Currently a data_dir variable is defined in path_def.py.

Setting this variable to the data folder eases defining file names to load for the analysis. However modifying the variable in path_def.py will be detected as a source code modification by git.

We need to provide a way for the user to set data_dir without modifying the FRETBursts sources.

A possible solution would be defining data_dir in the helper script load_fretbursts. The user will copy the script in his notebook folder (or will find it already there if downloading FRETBursts_notebooks). So modifying it will not touch the FRETBursts sources.

Another solution would be using some type of configuration file in the user folder, similar to what ipython does.

[tritemio]

When moving data_dir, remember to remove it from fretbursts.init.

[tritemio]

Another solution would be using a config file with configparser or configobj.

See also:

• https://wiki.python.org/moin/ConfigParserShootout
• http://stackoverflow.com/questions/7567642/where-to-put-a-configuration-file-in-python

[tritemio]

Or maybe, for now, define data_dir at the beginning of each notebook. Just because Explicit is better than implicit.