xml2xlsx 1.0.2
XML to XLSX converter
License: MIT
Keywords: xml lxml xlsx development

========
xml2xlsx
========

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Creating ``xlsx`` files from ``xml`` template using openpyxl_.

Target
======
This project is intended to create ``xlsx`` files from ``xml`` api to
``openpyxl``, supposedly generated by other tamplate engines (i.e. django,
jinja).

This is a merely an xml parser translating mostly linearly to worksheet, rows
and finally cells of the Excel workbook.

Example
-------
An xml file like this one

.. code-block:: xml

    <workbook>
        <worksheet title="test">
            <row><cell>This</cell><cell>is</cell><cell>a TEST</cell></row>
            <row><cell>Nice, isn't it?</cell></row>
        </worksheet>
    </workbook>

can be parsed to create a neat Excel workbook with two rows of data in one
worksheet. Parsing can be done using command line (provided that you have your
system paths set correctly:

.. code-block:: bash

    xml2xlsx < input.xml > output.xml

or as a library call

.. code-block:: python

    from xml2xlsx import xml2xlsx
    template = '<sheet title="test"></sheet>'
    f = open('test.xlsx', 'wb')
    f.write(xml2xlsx(template))
    f.close()

This is mainly intended (and was developed for this purpose) to parse files
generated by other templating engines, like django template system. One can
generate an excel workbook from template like this:

.. code-block:: xml

    {% for e in list %}
        <row><cell>{{ e.name }}</cell></row>
    {% endfor %}


Features
========
Basic features of the library include creating multiple, named sheets within one
workbook and creating rows of cells in these sheets. However, there are more
possibiliteis to create complex excel based reports.

Cell type
---------
Each cell can be specified to use one of the types:

* string (default)
* number
* date

Type is defined in ``type`` cell attribute. The cell value is converted
appropriately to the type specified. If you insert a number in the cell value
and do not specify ``type="number"`` attribute, you will find Excel complaining
about storing nubers as text.

Since there are more date formats than countries, you have to be aware of
current locale. The simplest way to be i18n compatible is to specify date format
in ``date-fmt`` attribute and pass compatible (possibily non localized) date
in the cell value, as in the following example

.. code-block:: xml

    ...
    <row><cell type="date" date-fmt="%Y-%m-%d">2016-10-01</cell></row>
    <row><cell type="date" date-fmt="%d.%m.%Y">01.10.2016</cell></row>
    ...

Generated excel file will have two rows with the same date (1st of October 2016)
with date formatted according to Excel defaults (and current locale).

.. warning::

    Excel tries to be very smart and converts date-like text to date format.
    Please use ``type="date"`` and ``date-fmt`` attribute always if you pass
    dates to cells.

Columns
-------
Columns can be tackled only in a limited way, i.e. only column widths can be
changed. Column properties are defined in ``columns`` tag as one or more child
of the ``sheet`` tag. It is possible to specify a range of columns using
``start`` and ``end`` atrributes. For example:

.. code-block:: xml

    ...
    <sheet title="test">
        <columns start="A" end="D" width="123"/>
        <row><cell>Test</cell></row>
    </sheet>
    ...


Formulas
--------
``xml2xls`` can effectively create cells with formulas in them. The only
limitation (as with ``openpyxl``) is using English names of the functions.

For example:

.. code-block:: xml

    ...
    <row><cell>=SUM(A1:A5)</cell></row>
    ...

Cell referencing
----------------
The parser can store positions of the cell in a dictionary-like structure. It
then can be referenced to create complex formulas. Each value of the cell is
preprocessed using string format with stored values. This means that these
values can be referenced using ``{`` and ``}`` brackets.

Current row and column
~~~~~~~~~~~~~~~~~~~~~~
There are two basic values that can always be used, i.e. ``row`` and ``col``
which return current row number and column name.

.. code-block:: xml

    <workbook>
        <sheet>
            <row><cell>{col}{row}</cell></row>
        </sheet>
    </workbook>
    ...

would create a workbook with a text "A1" included in the ``A1`` cell of the
worksheet. Using template languages, you can create more complicated
constructs, like (using django template system):

.. code-block:: xml

    ...
    {% for e in list %}
    <row>
        <cell type="date" date-fmt="%Y-%m-%d">{{ e|date:"Y-m-d" }}</cell>
        <cell>=TEXT(A{row}, "ddd")</cell>
    </row>
    {% endfor %}
    ...

would create a list of rows with a date in the first column and weekday names
for these dates in the second column (provided ``list`` context variable
contains a list of dates).

Specified cell
~~~~~~~~~~~~~~
It is also possible to store cell possible to store names of specified cells in
a pseudo-variable (as in a dictionary). One has to use ``ref-id`` attribute of
the ``cell`` tag and then reuse the value of this attribute in the remainder of
the xml input. This is very useful in formulas. A simple example would be
referencing another cell in a formula like this:

.. code-block:: xml

    ...
    <row><cell ref-id="mycell">This is just a test</cell></row>
    ...
    <row><cell>={mycell}</cell></row>
    ...

which would create an excel formula referencing a cell with "this is just a
test" text, whatever this cell address was.

.. warning::

    Using the same identifier in ``ref-id`` attribute for two different cells
    **overwrites** the cell reference, i.e. the last cell in the xml template
    would be referenced.

A more complex example using django template engine to create summaries can
look like this:

.. code-block:: xml

    ...
    {% for e in list %}
        <row>
            <cell ref-id="{% if forloop.first %}start{% elsif forloop.last %}end{% endif %}">
                {{ e }}
            </cell>
        </row>
    {% endfor %}
    <row>
        <cell>Summary</cell>
        <cell>=SUM({start}:{end})</cell>
    </row>
    ...

List of cells
~~~~~~~~~~~~~
Referencing a single cell can be harsh when dealing with complex reports.
Especially when creating summaries of irregularly sheet-distributed data.
``xml2xlsx`` can append a cell to a variable-like list, as in ``ref-id``
attribute, to reuse it as a comma concatenated value. Instead of ``ref-id``, one
has to use ``ref-append`` attribute.

This is a simple example to demonstrate the feature:

.. code-block::

    ...
    <sheet>
        <row>
            <cell ref-append="mylist">1</cell>
            <cell ref-append="mylist">2</cell>
        </row>
        <row><cell ref-append="mylist">3</cell></row>
        <row><cell>=SUM({mylist})</cell></row>
    </sheet>

This will generate an Excel sheet with ``A3`` cell containing formula to sum
``A1``, ``B1`` and ``A2`` cells (``=SUM(A1, B1, A2)``).

Referencing limitations
~~~~~~~~~~~~~~~~~~~~~~~
It is perfectly possible to reference a cell in another sheet with both
``ref-id`` and ``ref-append``. However, there is a limitation to that. Since
``xml2xslx`` is a linear parser, you are only allowed to reference already
parsed elements. This means, you have to create sheets in a proper order (sheets
referencing other sheets must be created **after** referenced cells are parsed).

The following example **will not work**:

.. code-block:: xml

    ...
    <sheet title="one">
        <row><cell>{mycell}</cell></row>
    </sheet>
    <sheet title="two">
        <row><cell ref-id="mycell">XYZ</cell></row>
    </sheet>
    ...

However, it is possible to make this exmaple work **and** retain the same
worksheet ordering using ``index`` attribute:

.. code-block:: xml

    ...
    <sheet title="two">
        <row><cell ref-id="mycell">XYZ</cell></row>
    </sheet>
    <sheet title="one" index="0">
        <row><cell>{mycell}</cell></row>
    </sheet>
    ...


Cell formatting
---------------
The cell format can be specified using various attributes of the cell tag. Only
font formatting can be specifed for now.

Font format
~~~~~~~~~~~
A font format is specified in in ``font`` attribute. It is a semicolon separated
dict like list of font formats as specified in
`font <http://openpyxl.readthedocs.io/en/default/api/openpyxl.styles.fonts.html#openpyxl.styles.fonts.Font>`_ class of
openpyxl_ library.

An example to create a cell with bold 10px font:

.. code-block::

    ...
    <cell font="bold: True; size: 10px;">Cell formatted</cell>
    ...


Planned features
----------------
Here is the (probably incomplete) wishlist for the project

* Global font and cell styles
* Row widths and column heights
* Horizontal and vertical cell merging
* XML validation with XSD to quickly raise an error if parsing wrong xml

XML Schema Reference
====================
Parsed xml should be enclosed in a ``workbook`` tag. Each ``workbook`` tag can
have multiple ``sheet``. The hierarchy continues to ``row`` and ``cell`` tags.

Here is a complete list of available attributes of these tags.

``workbook``
------------
No attributes for now.

``sheet``
---------

:Attribute:
    ``title``
:Usage:
    Specifies the worksheet title


:Attribute:
    ``index``
:Usage:
    Specifies the worksheet index. This is relative to already created indexes.
    An index of 0 creates sheet at the beginning of the sheets collection.

``row``
-------
No attributes for now


``columns``
-----------

:Attribute:
    ``start``
:Usage:
    Specifies the starting column for the column range (in a letter format).

:Attribute:
    ``end``
:Usage:
    Specifies the ending column for the column range (in a letter format).
:Default:
    Same as ``start`` attribute

:Attribute:
    ``width``
:Usage:
    Specifies the width for all columns in the range. It is in px format.


.. _cell:

``cell``
--------

:Attribute:
    ``type``
:Usage:
    Specifies the resulting type of the excel cell.
:Type:
    One of ``unicode``, ``date``, ``number``
:Default:
    ``unicode``


:Attribute:
    ``date-fmt``
:Usage:
    Specifies the format of the date parsed as in `strftime and strptime <https://docs.python.org/2/library/datetime.html#strftime-and-strptime-behavior>`_
    functions of ``datetime`` standard python library.
:Remarks:
    Parsed only if ``type="date"``.


:Attribute:
    ``font``
:Usage:
    Sepcifies font formatting for a single cell.
:Type:
    List of semicolon separated dict-like values in form of
    ``key: value; key: value;``
:Remarks:
    Key and values are arguments of ``Font`` clas in ``openpyxl``.

Release History
---------------

0.2
~~~

* Added documentation
* Added cell referencing with inter-sheet possibility
* Changed ``sheet`` title attribute from ``name`` to ``title``
* Added possibility to set index for a sheet


.. _openpyxl: https://bitbucket.org/openpyxl/openpyxl