path: root/docs/tutorial.rst

========
Tutorial
========

**This tutorial is distributed with PrettyTable and is meant to serve as
a "quick start" guide for the lazy or impatient. It is not an exhaustive
description of the whole API, and it is not guaranteed to be 100% up to
date. For more complete and update documentation, check the PrettyTable
wiki at http://code.google.com/p/prettytable/w/list**

Getting your data into (and out of) the table
=============================================

Let's suppose you have a shiny new PrettyTable:

::

    from prettytable import PrettyTable
    x = PrettyTable()

and you want to put some data into it. You have a few options.

Row by row
----------

You can add data one row at a time. To do this you can set the field
names first using the ``field_names`` attribute, and then add the rows
one at a time using the ``add_row`` method:

::

    x.field_names = ["City name", "Area", "Population", "Annual Rainfall"]
    x.add_row(["Adelaide",1295, 1158259, 600.5])
    x.add_row(["Brisbane",5905, 1857594, 1146.4])
    x.add_row(["Darwin", 112, 120900, 1714.7])
    x.add_row(["Hobart", 1357, 205556, 619.5])
    x.add_row(["Sydney", 2058, 4336374, 1214.8])
    x.add_row(["Melbourne", 1566, 3806092, 646.9])
    x.add_row(["Perth", 5386, 1554769, 869.4])

Column by column
----------------

You can add data one column at a time as well. To do this you use the
``add_column`` method, which takes two arguments - a string which is the
name for the field the column you are adding corresponds to, and a list
or tuple which contains the column data"

::

    x.add_column("City name",
    ["Adelaide","Brisbane","Darwin","Hobart","Sydney","Melbourne","Perth"])
    x.add_column("Area", [1295, 5905, 112, 1357, 2058, 1566, 5386])
    x.add_column("Population", [1158259, 1857594, 120900, 205556, 4336374, 3806092,
    1554769])
    x.add_column("Annual Rainfall",[600.5, 1146.4, 1714.7, 619.5, 1214.8, 646.9,
    869.4])

Mixing and matching
-------------------

If you really want to, you can even mix and match ``add_row`` and
``add_column`` and build some of your table in one way and some of it in
the other. There's a unit test which makes sure that doing things this
way will always work out nicely as if you'd done it using just one of
the two approaches. Tables built this way are kind of confusing for
other people to read, though, so don't do this unless you have a good
reason.

Importing data from a CSV file
------------------------------

If you have your table data in a comma separated values file (.csv), you
can read this data into a PrettyTable like this:

::

    from prettytable import from_csv
    fp = open("myfile.csv", "r")
    mytable = from_csv(fp)
    fp.close()

Importing data from a database cursor
-------------------------------------

If you have your table data in a database which you can access using a
library which confirms to the Python DB-API (e.g. an SQLite database
accessible using the sqlite module), then you can build a PrettyTable
using a cursor object, like this:

::

    import sqlite3
    from prettytable import from_db_cursor

    connection = sqlite3.connect("mydb.db")
    cursor = connection.cursor()
    cursor.execute("SELECT field1, field2, field3 FROM my_table")
    mytable = from_db_cursor(cursor)

Getting data out
----------------

There are three ways to get data out of a PrettyTable, in increasing
order of completeness:

-  The ``del_row`` method takes an integer index of a single row to
   delete.
-  The ``clear_rows`` method takes no arguments and deletes all the rows
   in the table - but keeps the field names as they were so you that you
   can repopulate it with the same kind of data.
-  The ``clear`` method takes no arguments and deletes all rows and all
   field names. It's not quite the same as creating a fresh table
   instance, though - style related settings, discussed later, are
   maintained.

Displaying your table in ASCII form
===================================

PrettyTable's main goal is to let you print tables in an attractive
ASCII form, like this:

::

    +-----------+------+------------+-----------------+
    | City name | Area | Population | Annual Rainfall |
    +-----------+------+------------+-----------------+
    | Adelaide  | 1295 |  1158259   |      600.5      |
    | Brisbane  | 5905 |  1857594   |      1146.4     |
    | Darwin    | 112  |   120900   |      1714.7     |
    | Hobart    | 1357 |   205556   |      619.5      |
    | Melbourne | 1566 |  3806092   |      646.9      |
    | Perth     | 5386 |  1554769   |      869.4      |
    | Sydney    | 2058 |  4336374   |      1214.8     |
    +-----------+------+------------+-----------------+

You can print tables like this to ``stdout`` or get string
representations of them.

Printing
--------

To print a table in ASCII form, you can just do this:

::

    print x

in Python 2.x or:

::

    print(x)

in Python 3.x.

The old x.printt() method from versions 0.5 and earlier has been
removed.

To pass options changing the look of the table, use the get\_string()
method documented below:

::

    print x.get_string()

Stringing
---------

If you don't want to actually print your table in ASCII form but just
get a string containing what *would* be printed if you use "print x",
you can use the ``get_string`` method:

::

    mystring = x.get_string()

This string is guaranteed to look exactly the same as what would be
printed by doing "print x". You can now do all the usual things you can
do with a string, like write your table to a file or insert it into a
GUI.

Controlling which data gets displayed
-------------------------------------

If you like, you can restrict the output of ``print x`` or
``x.get_string`` to only the fields or rows you like.

The ``fields`` argument to these methods takes a list of field names to
be printed:

::

    print x.get_string(fields=["City name", "Population"])

gives:

::

    +-----------+------------+
    | City name | Population |
    +-----------+------------+
    | Adelaide  |  1158259   |
    | Brisbane  |  1857594   |
    | Darwin    |   120900   |
    | Hobart    |   205556   |
    | Melbourne |  3806092   |
    | Perth     |  1554769   |
    | Sydney    |  4336374   |
    +-----------+------------+

The ``start`` and ``end`` arguments take the index of the first and last
row to print respectively. Note that the indexing works like Python list
slicing - to print the 2nd, 3rd and 4th rows of the table, set ``start``
to 1 (the first row is row 0, so the second is row 1) and set ``end`` to
4 (the index of the 4th row, plus 1):

::

    print x.get_string(start=1,end=4)

prints:

::

    +-----------+------+------------+-----------------+
    | City name | Area | Population | Annual Rainfall |
    +-----------+------+------------+-----------------+
    | Brisbane  | 5905 |    1857594 | 1146.4          |
    | Darwin    | 112  |     120900 | 1714.7          |
    | Hobart    | 1357 |     205556 | 619.5           |
    +-----------+------+------------+-----------------+

Changing the alignment of columns
---------------------------------

By default, all columns in a table are centre aligned.

All columns at once
~~~~~~~~~~~~~~~~~~~

You can change the alignment of all the columns in a table at once by
assigning a one character string to the ``align`` attribute. The allowed
strings are "l", "r" and "c" for left, right and centre alignment,
respectively:

::

    x.align = "r"
    print x

gives:

::

    +-----------+------+------------+-----------------+
    | City name | Area | Population | Annual Rainfall |
    +-----------+------+------------+-----------------+
    |  Adelaide | 1295 |    1158259 |           600.5 |
    |  Brisbane | 5905 |    1857594 |          1146.4 |
    |    Darwin |  112 |     120900 |          1714.7 |
    |    Hobart | 1357 |     205556 |           619.5 |
    | Melbourne | 1566 |    3806092 |           646.9 |
    |     Perth | 5386 |    1554769 |           869.4 |
    |    Sydney | 2058 |    4336374 |          1214.8 |
    +-----------+------+------------+-----------------+

One column at a time
~~~~~~~~~~~~~~~~~~~~

You can also change the alignment of individual columns based on the
corresponding field name by treating the ``align`` attribute as if it
were a dictionary.

::

    x.align["City name"] = "l"
    x.align["Area"] = "c"
    x.align["Population"] = "r"
    x.align["Annual Rainfall"] = "c"
    print x

gives:

::

    +-----------+------+------------+-----------------+
    | City name | Area | Population | Annual Rainfall |
    +-----------+------+------------+-----------------+
    | Adelaide  | 1295 |    1158259 |      600.5      |
    | Brisbane  | 5905 |    1857594 |      1146.4     |
    | Darwin    | 112  |     120900 |      1714.7     |
    | Hobart    | 1357 |     205556 |      619.5      |
    | Melbourne | 1566 |    3806092 |      646.9      |
    | Perth     | 5386 |    1554769 |      869.4      |
    | Sydney    | 2058 |    4336374 |      1214.8     |
    +-----------+------+------------+-----------------+

Sorting your table by a field
-----------------------------

You can make sure that your ASCII tables are produced with the data
sorted by one particular field by giving ``get_string`` a ``sortby``
keyword argument, which > must be a string containing the name of one
field.

For example, to print the example table we built earlier of Australian
capital city data, so that the most populated city comes last, we can do
this:

::

    print x.get_string(sortby="Population")

to get

::

    +-----------+------+------------+-----------------+
    | City name | Area | Population | Annual Rainfall |
    +-----------+------+------------+-----------------+
    | Darwin    | 112  |   120900   |      1714.7     |
    | Hobart    | 1357 |   205556   |      619.5      |
    | Adelaide  | 1295 |  1158259   |      600.5      |
    | Perth     | 5386 |  1554769   |      869.4      |
    | Brisbane  | 5905 |  1857594   |      1146.4     |
    | Melbourne | 1566 |  3806092   |      646.9      |
    | Sydney    | 2058 |  4336374   |      1214.8     |
    +-----------+------+------------+-----------------+

If we want the most populated city to come *first*, we can also give a
``reversesort=True`` argument.

If you *always* want your tables to be sorted in a certain way, you can
make the setting long term like this:

::

    x.sortby = "Population"
    print x
    print x
    print x

All three tables printed by this code will be sorted by population (you
could do ``x.reversesort = True`` as well, if you wanted). The behaviour
will persist until you turn it off:

::

    x.sortby = None

If you want to specify a custom sorting function, you can use the
``sort_key`` keyword argument. Pass this a function which accepts two
lists of values and returns a negative or positive value depending on
whether the first list should appeare before or after the second one. If
your table has n columns, each list will have n+1 elements. Each list
corresponds to one row of the table. The first element will be whatever
data is in the relevant row, in the column specified by the ``sort_by``
argument. The remaining n elements are the data in each of the table's
columns, in order, including a repeated instance of the data in the
``sort_by`` column.

Changing the appearance of your table - the easy way
====================================================

By default, PrettyTable produces ASCII tables that look like the ones
used in SQL database shells. But if can print them in a variety of other
formats as well. If the format you want to use is common, PrettyTable
makes this very easy for you to do using the ``set_style`` method. If
you want to produce an uncommon table, you'll have to do things slightly
harder (see later).

Setting a table style
---------------------

You can set the style for your table using the ``set_style`` method
before any calls to ``print`` or ``get_string``. Here's how to print a
table in a format which works nicely with Microsoft Word's "Convert to
table" feature:

::

    from prettytable import MSWORD_FRIENDLY
    x.set_style(MSWORD_FRIENDLY)
    print x

In addition to ``MSWORD_FRIENDLY`` there are currently two other
in-built styles you can use for your tables:

-  ``DEFAULT`` - The default look, used to undo any style changes you
   may have made
-  ``PLAIN_COLUMNS`` - A borderless style that works well with command
   line programs for columnar data

Other styles are likely to appear in future releases.

Changing the appearance of your table - the hard way
====================================================

If you want to display your table in a style other than one of the
in-built styles listed above, you'll have to set things up the hard way.

Don't worry, it's not really that hard!

Style options
-------------

PrettyTable has a number of style options which control various aspects
of how tables are displayed. You have the freedom to set each of these
options individually to whatever you prefer. The ``set_style`` method
just does this automatically for you.

The options are these:

-  ``border`` - A boolean option (must be ``True`` or ``False``).
   Controls whether > > or not a border is drawn around the table.
-  ``header`` - A boolean option (must be ``True`` or ``False``).
   Controls whether > > or not the first row of the table is a header
   showing the names of all the > > fields.
-  ``hrules`` - Controls printing of horizontal rules after rows.
   Allowed > > values: FRAME, HEADER, ALL, NONE - note that these are
   variables defined > > inside the ``prettytable`` module so make sure
   you import them or use > > ``prettytable.FRAME`` etc.
-  ``vrules`` - Controls printing of vertical rules between columns.
   Allowed > > values: FRAME, ALL, NONE.
-  ``int_format`` - A string which controls the way integer data is
   printed. > > This works like: ``print "%<int_format>d" % data``
-  ``float_format`` - A string which controls the way floating point
   data is > > printed. This works like:
   ``print "%<int_format>f" % data``
-  ``padding_width`` - Number of spaces on either side of column data
   (only used > > if left and right paddings are None).
-  ``left_padding_width`` - Number of spaces on left hand side of column
   data.
-  ``right_padding_width`` - Number of spaces on right hand side of
   column data.
-  ``vertical_char`` - Single character string used to draw vertical
   lines. > > Default is ``|``.
-  ``horizontal_char`` - Single character string used to draw horizontal
   lines. > > Default is ``-``.
-  ``junction_char`` - Single character string used to draw line
   junctions. > > Default is ``+``.

You can set the style options to your own settings in two ways:

Setting style options for the long term
---------------------------------------

If you want to print your table with a different style several times,
you can set your option for the "long term" just by changing the
appropriate attributes. If you never want your tables to have borders
you can do this:

::

    x.border = False
    print x
    print x
    print x

Neither of the 3 tables printed by this will have borders, even if you
do things like add extra rows inbetween them. The lack of borders will
last until you do:

::

    x.border = True

to turn them on again. This sort of long term setting is exactly how
``set_style`` works. ``set_style`` just sets a bunch of attributes to
pre-set values for you.

Note that if you know what style options you want at the moment you are
creating your table, you can specify them using keyword arguments to the
constructor. For example, the following two code blocks are equivalent:

::

    x = PrettyTable()
    x.border = False
    x.header = False
    x.padding_width = 5

x = PrettyTable(border=False, header=False, padding\_width=5)

Changing style options just once
--------------------------------

If you don't want to make long term style changes by changing an
attribute like in the previous section, you can make changes that last
for just one ``get_string`` by giving those methods keyword arguments.
To print two "normal" tables with one borderless table between them, you
could do this:

::

    print x
    print x.get_string(border=False)
    print x

Displaying your table in HTML form
==================================

PrettyTable will also print your tables in HTML form, as ``<table>``\ s.
Just like in ASCII form, you can actually print your table - just use
``print_html()`` - or get a string representation - just use
``get_html_string()``. HTML printing supports the ``fields``, ``start``,
``end``, ``sortby`` and ``reversesort`` arguments in exactly the same
way as ASCII printing.

Styling HTML tables
-------------------

By default, PrettyTable outputs HTML for "vanilla" tables. The HTML code
is quite simple. It looks like this:

::

    <table>
        <tr>
            <th>City name</th>
            <th>Area</th>
            <th>Population</th>
            <th>Annual Rainfall</th>
        </tr>
        <tr>
            <td>Adelaide</td>
            <td>1295</td>
            <td>1158259</td>
            <td>600.5</td>
        <tr>
            <td>Brisbane</td>
            <td>5905</td>
            <td>1857594</td>
            <td>1146.4</td>
        ...
        ...
        ...
    </table>

If you like, you can ask PrettyTable to do its best to mimick the style
options that your table has set using inline CSS. This is done by giving
a ``format=True`` keyword argument to either the ``print_html`` or
``get_html_string`` methods. Note that if you *always* want to print
formatted HTML you can do:

::

    x.format = True

and the setting will persist until you turn it off.

Just like with ASCII tables, if you want to change the table's style for
just one ``print_html`` or one ``get_html_string`` you can pass those
methods keyword arguments - exactly like ``print`` and ``get_string``.

Setting HTML attributes
-----------------------

You can provide a dictionary of HTML attribute name/value pairs to the
``print_html`` and ``get_html_string`` methods using the ``attributes``
keyword argument. This lets you specify common HTML attributes like
``name``, ``id`` and ``class`` that can be used for linking to your
tables or customising their appearance using CSS. For example:

::

    x.print_html(attributes={"name":"my_table", "class":"red_table"})

will print:

::

    <table name="my_table" class="red_table">
        <tr>
            <th>City name</th>
            <th>Area</th>
            <th>Population</th>
            <th>Annual Rainfall</th>
        </tr>
        ...
        ...
        ...
    </table>

Miscellaneous things
====================

Copying a table
---------------

You can call the ``copy`` method on a PrettyTable object without
arguments to return an identical independent copy of the table.

If you want a copy of a PrettyTable object with just a subset of the
rows, you can use list slicing notation:

::

    new_table = old_table[0:5]