.. include:: references.txt
.. _fixed_width_gallery:
Fixed-width Gallery
-------------------
Fixed-width tables are those where each column has the same width for every row
in the table. This is commonly used to make tables easy to read for humans or
FORTRAN codes. It also reduces issues with quoting and special characters,
for example::
Col1 Col2 Col3 Col4
---- --------- ---- ----
1.2 "hello" 1 a
2.4 's worlds 2 2
There are a number of common variations in the formatting of fixed-width tables
which :mod:`astropy.io.ascii` can read and write. The most signicant difference is
whether there is no header line (:class:`~astropy.io.ascii.FixedWidthNoHeader`), one
header line (:class:`~astropy.io.ascii.FixedWidth`), or two header lines
(:class:`~astropy.io.ascii.FixedWidthTwoLine`). Next, there are variations in the
delimiter character, whether the delimiter appears on either end ("bookends"),
and padding around the delimiter.
Details are available in the class API documentation, but the easiest way to
understand all the options and their interactions is by example.
Reading
^^^^^^^
FixedWidth
""""""""""
**Nice, typical fixed format table**
::
>>> from astropy.io import ascii
>>> table = """
... # comment (with blank line above)
... | Col1 | Col2 |
... | 1.2 | "hello" |
... | 2.4 |'s worlds|
... """
>>> ascii.read(table, Reader=ascii.FixedWidth)
rec.array([(1.2, '"hello"'), (2.4, "'s worlds")],
dtype=[('Col1', '<f8'), ('Col2', '|S9')])
**Typical fixed format table with col names provided**
::
>>> table = """
... # comment (with blank line above)
... | Col1 | Col2 |
... | 1.2 | "hello" |
... | 2.4 |'s worlds|
... """
>>> ascii.read(table, Reader=ascii.FixedWidth, names=('name1', 'name2'))
rec.array([(1.2, '"hello"'), (2.4, "'s worlds")],
dtype=[('name1', '<f8'), ('name2', '|S9')])
**Weird input table with data values chopped by col extent**
::
>>> table = """
... Col1 | Col2 |
... 1.2 "hello"
... 2.4 sdf's worlds
... """
>>> ascii.read(table, Reader=ascii.FixedWidth)
rec.array([(1.2, '"hel'), (2.4, "df's wo")],
dtype=[('Col1', '<f8'), ('Col2', '|S7')])
**Table with double delimiters**
::
>>> table = """
... || Name || Phone || TCP||
... | John | 555-1234 |192.168.1.10X|
... | Mary | 555-2134 |192.168.1.12X|
... | Bob | 555-4527 | 192.168.1.9X|
... """
>>> ascii.read(table, Reader=ascii.FixedWidth)
rec.array([('John', '555-1234', '192.168.1.10'),
('Mary', '555-2134', '192.168.1.12'),
('Bob', '555-4527', '192.168.1.9')],
dtype=[('Name', '|S4'), ('Phone', '|S8'), ('TCP', '|S12')])
**Table with space delimiter**
::
>>> table = """
... Name --Phone- ----TCP-----
... John 555-1234 192.168.1.10
... Mary 555-2134 192.168.1.12
... Bob 555-4527 192.168.1.9
... """
>>> ascii.read(table, Reader=ascii.FixedWidth, delimiter=' ')
rec.array([('John', '555-1234', '192.168.1.10'),
('Mary', '555-2134', '192.168.1.12'),
('Bob', '555-4527', '192.168.1.9')],
dtype=[('Name', '|S4'), ('--Phone-', '|S8'), ('----TCP-----', '|S12')])
**Table with no header row and auto-column naming.**
Use header_start and data_start keywords to indicate no header line.
::
>>> table = """
... | John | 555-1234 |192.168.1.10|
... | Mary | 555-2134 |192.168.1.12|
... | Bob | 555-4527 | 192.168.1.9|
... """
>>> ascii.read(table, Reader=ascii.FixedWidth,
... header_start=None, data_start=0)
rec.array([('John', '555-1234', '192.168.1.10'),
('Mary', '555-2134', '192.168.1.12'),
('Bob', '555-4527', '192.168.1.9')],
dtype=[('col1', '|S4'), ('col2', '|S8'), ('col3', '|S12')])
**Table with no header row and with col names provided.**
Second and third rows also have hanging spaces after final "|". Use header_start and data_start
keywords to indicate no header line.
::
>>> table = ["| John | 555-1234 |192.168.1.10|"
... "| Mary | 555-2134 |192.168.1.12| "
... "| Bob | 555-4527 | 192.168.1.9| "]
>>> ascii.read(table, Reader=ascii.FixedWidth,
... header_start=None, data_start=0,
... names=('Name', 'Phone', 'TCP'))
rec.array([('John', '555-1234', '192.168.1.10')],
dtype=[('Name', '|S4'), ('Phone', '|S8'), ('TCP', '|S12')])
FixedWidthNoHeader
""""""""""""""""""
**Table with no header row and auto-column naming. Use the FixedWidthNoHeader
convenience class.**
::
>>> table = """
... | John | 555-1234 |192.168.1.10|
... | Mary | 555-2134 |192.168.1.12|
... | Bob | 555-4527 | 192.168.1.9|
... """
>>> ascii.read(table, Reader=ascii.FixedWidthNoHeader)
rec.array([('John', '555-1234', '192.168.1.10'),
('Mary', '555-2134', '192.168.1.12'),
('Bob', '555-4527', '192.168.1.9')],
dtype=[('col1', '|S4'), ('col2', '|S8'), ('col3', '|S12')])
**Table with no delimiter with column start and end values specified.**
This uses the col_starts and col_ends keywords. Note that the
col_ends values are inclusive so a position range of 0 to 5
will select the first 6 characters.
::
>>> table = """
... # 5 9 17 18 28 <== Column start / end indexes
... # | | || | <== Column separation positions
... John 555- 1234 192.168.1.10
... Mary 555- 2134 192.168.1.12
... Bob 555- 4527 192.168.1.9
... """
>>> ascii.read(table, Reader=ascii.FixedWidthNoHeader,
... names=('Name', 'Phone', 'TCP'),
... col_starts=(0, 9, 18),
... col_ends=(5, 17, 28),
... )
rec.array([('John', '555- 1234', '192.168.1.'),
('Mary', '555- 2134', '192.168.1.'),
('Bob', '555- 4527', '192.168.1')],
dtype=[('Name', '|S4'), ('Phone', '|S9'), ('TCP', '|S10')])
FixedWidthTwoLine
"""""""""""""""""
**Typical fixed format table with two header lines with some cruft**
::
>>> table = """
... Col1 Col2
... ---- ---------
... 1.2xx"hello"
... 2.4 's worlds
... """
>>> ascii.read(table, Reader=ascii.FixedWidthTwoLine)
rec.array([(1.2, '"hello"'), (2.4, "'s worlds")],
dtype=[('Col1', '<f8'), ('Col2', '|S9')])
**Restructured text table**
::
>>> table = """
... ======= ===========
... Col1 Col2
... ======= ===========
... 1.2 "hello"
... 2.4 's worlds
... ======= ===========
... """
>>> ascii.read(table, Reader=ascii.FixedWidthTwoLine,
... header_start=1, position_line=2, data_end=-1)
rec.array([(1.2, '"hello"'), (2.4, "'s worlds")],
dtype=[('Col1', '<f8'), ('Col2', '|S9')])
**Text table designed for humans and test having position line before the header line.**
::
>>> table = """
... +------+----------+
... | Col1 | Col2 |
... +------|----------+
... | 1.2 | "hello" |
... | 2.4 | 's worlds|
... +------+----------+
... """
>>> ascii.read(table, Reader=ascii.FixedWidthTwoLine, delimiter='+',
... header_start=1, position_line=0, data_start=3, data_end=-1)
rec.array([(1.2, '"hello"'), (2.4, "'s worlds")],
dtype=[('Col1', '<f8'), ('Col2', '|S9')])
Writing
^^^^^^^
FixedWidth
""""""""""
**Define input values ``dat`` for all write examples.**
::
>>> table = """
... | Col1 | Col2 | Col3 | Col4 |
... | 1.2 | "hello" | 1 | a |
... | 2.4 | 's worlds | 2 | 2 |
... """
>>> dat = ascii.read(table, Reader=ascii.FixedWidth)
**Write a table as a normal fixed width table.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidth)
| Col1 | Col2 | Col3 | Col4 |
| 1.2 | "hello" | 1 | a |
| 2.4 | 's worlds | 2 | 2 |
**Write a table as a fixed width table with no padding.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidth, delimiter_pad=None)
|Col1| Col2|Col3|Col4|
| 1.2| "hello"| 1| a|
| 2.4|'s worlds| 2| 2|
**Write a table as a fixed width table with no bookend.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidth, bookend=False)
Col1 | Col2 | Col3 | Col4
1.2 | "hello" | 1 | a
2.4 | 's worlds | 2 | 2
**Write a table as a fixed width table with no delimiter.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidth, bookend=False, delimiter=None)
Col1 Col2 Col3 Col4
1.2 "hello" 1 a
2.4 's worlds 2 2
**Write a table as a fixed width table with no delimiter and formatting.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidth,
... formats={'Col1': '%-8.3f', 'Col2': '%-15s'})
| Col1 | Col2 | Col3 | Col4 |
| 1.200 | "hello" | 1 | a |
| 2.400 | 's worlds | 2 | 2 |
FixedWidthNoHeader
""""""""""""""""""
**Write a table as a normal fixed width table.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthNoHeader)
| 1.2 | "hello" | 1 | a |
| 2.4 | 's worlds | 2 | 2 |
**Write a table as a fixed width table with no padding.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthNoHeader, delimiter_pad=None)
|1.2| "hello"|1|a|
|2.4|'s worlds|2|2|
**Write a table as a fixed width table with no bookend.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthNoHeader, bookend=False)
1.2 | "hello" | 1 | a
2.4 | 's worlds | 2 | 2
**Write a table as a fixed width table with no delimiter.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthNoHeader, bookend=False,
... delimiter=None)
1.2 "hello" 1 a
2.4 's worlds 2 2
FixedWidthTwoLine
"""""""""""""""""
**Write a table as a normal fixed width table.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthTwoLine)
Col1 Col2 Col3 Col4
---- --------- ---- ----
1.2 "hello" 1 a
2.4 's worlds 2 2
**Write a table as a fixed width table with space padding and '=' position_char.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthTwoLine,
... delimiter_pad=' ', position_char='=')
Col1 Col2 Col3 Col4
==== ========= ==== ====
1.2 "hello" 1 a
2.4 's worlds 2 2
**Write a table as a fixed width table with no bookend.**
::
>>> ascii.write(dat, Writer=ascii.FixedWidthTwoLine, bookend=True, delimiter='|')
|Col1| Col2|Col3|Col4|
|----|---------|----|----|
| 1.2| "hello"| 1| a|
| 2.4|'s worlds| 2| 2|
