# Changes in version 1.5

With version 1.5 we introduced several changes on the library as well as on the data model side (nix model version 1.2). Some of these changes are breaking changes. That is, you may need to adapt your code. Or convert files (see below).

Files written with nixpy versions < 1.5 (model version 1.1) can be opened for reading but not for writing. Trying to do so will lead to an exception:

    import nixio
    print("Opening in ReadOnly mode is possible.")
    nixfile = nixio.File.open("old_format_file.nix", nixio.FileMode.ReadOnly)
    print("file format version:", f.version)

    print("Opening in ReadWrite model will fail:")
    nixfile = nixio.File.open("old_format_file.nix", nixio.FileMode.ReadWrite)

    Opening in ReadOnly mode is possible.
    File format version: (1, 1, 0)
    Opening in ReadWrite model will fail:
        159         if mode == FileMode.ReadWrite:
        160             if not can_write(self):
    --> 161                 raise RuntimeError("Cannot open file for writing. "
        162                                    "Incompatible version.")
        163         elif mode == FileMode.ReadOnly:

        RuntimeError: Cannot open file for writing. Incompatible version.

You may want to convert such files using the `nixio` command line tool that comes with the library.

    nixio upgrade --help

Or implement conversion into your code:

    import nixio
    filename = "test.nix"
    nixio.file_upgrade(filename, quiet=False)

Pass `quiet=False` in order to get some feedback on what the tool did. Note: Files are replaced *in place*. Make sure to backup your files before upgrading.

## Model changes

- the metadata model was simplified to reflect the changes introduced to the underlying odml data model. Accordingly the Value entity does no longer exist. New versions of the library can read but not write old data. Experience showed that almost all use cases stored single Values in a Property. The overhead (code and also file size) of keeping each value in a separate Entity is not justified. The Property now keeps all information that was Value related, such as the uncertainty. If you want to store multiple values in a property this is still possible but they have to have the same data type. (see Annotations with arbitrary metadata for more information).

- New DataFrame entity that stores tabular data. Each column has a name, unit, and data type. (see The DataFrame for more information).

- Tags and MultiTags can link to DataFrames as features.

- RangeDimensions ticks can now be stored within the dimension descriptor, or in linked DataArrays or DataFrames. Ticks must still be one-dimensional (see RangeDimension for more information).

- Because of the above change, the former AliasRangeDimension is no longer needed. The same functionality is achieved by linking the RangeDimension to the DataArray itself.

## API changes

- `DataArray.append_alias_range_dimension` has been removed. Use `DataArray.append_range_dimension_using_self` for the same effect.

- `SampledDimension.axis` can now be called with an optional argument `start_position` to get an axis that starts at the given position. Starting at a given index is still possible.

- `Block.create_data_array` has additional keyword-arguments to directly provide label and unit.

## Misc

Extended command line tool abilities; The `nixio` command line tool now bundles commands for validating files, upgrading old files to the current version, and to explore file content.

    nixio --help

    usage: nixio [-h] {explore,validate,upgrade}

    Command line interface for nixio tools

    optional arguments:
    -h, --help            show this help message and exit

    commands:
    {explore,validate,upgrade}
       explore             Search for information within NIX file(s). Use the "file" command for general
                            information about the file(s). The verbose flag can be used to get more detailed
                            information about the file structure. Multiple -v options increase the
                            verbosity. (e.g. 'nixio explore file nix_file -vvv' for most detailed output).
                            The "metadata" (mdata) and "data" commands provide further options for finding
                            and viewing data and metadata information. With the "dump" subcommand data can
                            be dumped to file (up to 3D data). The "plot" command is only available if the
                            nixworks package is installed (https://github.com/G-node/nixworks). NOTE: This
                            tool is under active development. Please use the github issue tracker
                            (https://github.com/G-node/nixpy/issues) for bug reports and feature requests.
       validate            Validate NIX files for missing or inconsistent objects and annotations.
       upgrade             Upgrade NIX files to newest file format version.