Formatting text in tabular form with Python

Question

propertiesTextBlock = """
    Basic Properties
    ----------------
    - nodes (n)         {n}
    - edges (m)         {m}
    - min. degree           {minDeg}
    - max. degree           {maxDeg}
    - isolated nodes        {isolates}
    - self-loops            {loops}
    - density           {dens:10.6f}
"""

Several data items are inserted using string.format. Output to console then looks like:

Basic Properties
----------------
- nodes (n)         10680
- edges (m)         24316
- min. degree           1
- max. degree           205
- isolated nodes        0
- self-loops            0
- density             0.000426

Not perfect, because I need to manually insert exactly the right amount of tabs in the text block. Also, what if I want to align the numbers differently (e.g right-justify everything, align at . ...) Is there an easy way to make sure that this table looks nice?

Are you ok to use [prettytable](https://code.google.com/p/prettytable/) format instead of this tabular form? — alecxe, Aug 14 '13 at 13:13
@alecxe Ideally, I want the output to be in markdown format. Is prettytable compatible with that? — clstaudt, Aug 14 '13 at 13:17
You do know that the format syntax supports aligning text left or right? — Martijn Pieters, Aug 14 '13 at 13:18
@cls also take a look at [tabulate](https://bitbucket.org/astanin/python-tabulate) module, might help. — alecxe, Aug 14 '13 at 13:21
@cls: I made that into an answer below; it was getting a little too verbose for a comment. :-) — Martijn Pieters, Aug 14 '13 at 13:38

Martijn Pieters · Answer 1 · 2013-08-14T14:55:14.300

You can use the format mini language to specify alignments:

>>> print '- nodes (n) {n:>20}\n- edges (m) {m:>20}'.format(n=1234, m=234)
- nodes (n)                 1234
- edges (m)                  234

The >20 formatting specification sets the field width to 20 characters and right-aligns the value in that field.

This does not support alignment by decimal point, however. You can specify dynamic field widths though:

>>> print '- nodes (n) {n:>{width}}'.format(n=123, width=5)
- nodes (n)   123
>>> print '- nodes (n) {n:>{width}}'.format(n=123, width=10)
- nodes (n)        123

which you can adapt to add or remove whitespace around a floating point number:

>>> from math import log10
>>> print '- density {density:>{width}.6f}'.format(density=density, width=10-int(log10(int(density))))
- density  0.000426
>>> density = 10.000426
>>> print '- density {density:>{width}.6f}'.format(density=density, width=10-int(log10(int(density))))
- density 10.000426

Here the field width is adjusted to shift the decimal point left or right based on how much space the whole value is going to take. Note that the field width is the total width, so including the decimal point and the 6 decimals.

score 1 · Answer 2 · edited Aug 14 '13 at 13:51

The right answer is maybe to use prettytable or tabulate.

If you want to stay with plain old format, you could control field width:

>>> print "node:{0:16}".format(10680,);
node:           10680
#    ^^^^^^^^^^^^^^^^ 
#      16 characters

For float values you could align to the decimal point:

>>> print "node:{0:16.2f}".format(10680.); \
... print "node:{0:16.2f}".format(10.5)
... print "node:{0:16.2f}".format(123.456)
node:        10680.00
node:           10.50
node:          123.46
#    ^^^^^^^^^^^^^^^^ 
#      16 characters

Here is the formal description of the "format mini-language": http://docs.python.org/2/library/string.html#formatstrings

Formatting text in tabular form with Python

2 Answers2

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