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# Frequently Asked Questions

## How does the documentation work?

The InaSAFE documentation files are written using the RST format (quickreference guide) and stored with the source code in github:

    https://github.com/AIFDR/inasafe/tree/master/docs/source

The RST files are used for two products:
  - HTML files generated using Sphinx (http://sphinx.pocoo.org) by running https://github.com/AIFDR/inasafe/blob/master/docs/Makefile. These files are accessible through both the file browser and the help button available in InaSAFE
  - The web site http://readthedocs.org/docs/inasafe which automatically reads the RST files from github to update its content. The steps to achieve this are
  1. Register the project on the dashboard at ReadTheDocs (http://readthedocs.org/dashboard/inasafe/edit). In particular, this form points to the github repository where the RST files reside.
  2. Either manually build the project by clicking ‘Build latest version’ on http://readthedocs.org/dashboard/inasafe/ or by activating the service hook for ReadTheDocs at github: https://github.com/AIFDR/inasafe/admin/hooks

## How do I replace a string across multiple files

To replace string layer_type, say, with layertype across all python files in project, do:

    find . -name "*.py" -print | xargs sed -i 's/layer_type/layertype/g'

Alternative you can install the ‘rpl’ command line tool:

    sudo apt-get install rpl

Using rpl is much simpler, just do:

    rpl "oldstring" "newstring" *.py

For details on the find command see this article.

## How did you embed the git version SHA1 into each .py file?

The format was derived using the git log format tag. It is stored in the source of each python as:

    __revision__ = '$Format:%H$'

‘%H’ being the format tag for the SHA1. The __revision__ is not updated with each commit. Rather is is registered with git for replacement when using git-archive by doing this:

    echo "*.py export-subst" > .gitattributes
    git add .gitattributes

The above only needs to be done once and then all python files with format substitutions will be replaced when running git-archive. The actual substition takes place at the time that a git archive is generated (git archive creates a copy of the repo with all repository metadata stripped out). For example:

    git archive version-0_3 | tar -x -C /tmp/inasafe-0.3.0

You can verify SHA1 replacement has been made by doing:

    cat /tmp/inasafe/gui/is_plugin.py | grep revision
    __revision__ = 'a515345e43b25d065e1ae0d73687c13531ea4c9c'

The deployment of version tagged files is automated by using the `scriptsrelease.sh` script.

## How do you profile code?

sudo apt-get install python-profiler python -m cProfile -s time safe/common/test_polygon.py

and

sudo easy_install pycallgraph sudo apt-get install graphviz pycallgraph safe/common/test_polygon.py

See also http://stackoverflow.com/questions/582336/how-can-you-profile-a-python-script

## Why do I got 1e+24 (or another big number) instead of NaN when I saved vector files?

InaSAFE needs to convert NaN to 1e+24 or more specifically 24 digits of 9 because NaN is not intepreted correclty on Windows. You can read more information about it on http://trac.osgeo.org/gdal/ticket/4799 or in Github issue #269.

But don’t worry, when InaSAFE read vector file, it will convert the 1e+24 back to NaN. So, any computation inside InaSAFE will treat NaN as NaN in numpy.

Note

You’ll need to convert the 1e+24 to NaN value manually if you want to use it without InaSAFE.

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