Pretty printing a list of list of floats?

Basically i have to dump a series of temperature readings, into a text file. This is a space delimited list of elements, where each row represents something (i don't know, and it just gets forced into a fortran model, shudder). I am more or less handling it from our groups side, which is extracting those temperature readings and dumping them into a text file.

Basically a quick example is i have a list like this(but with alot more elements):

temperature_readings = [ [1.343, 348.222, 484844.3333], [12349.000002, -2.43333]]

In the past we just dumped this into a file, unfortunately there is some people who have this irritating kna开发者_如何学JAVAck of wanting to look directly at the text file, and picking out certain columns and changing some things (for testing.. i don't really know..). But they always complain about the columns not lining up properly, they pretty much the above list to be printed like this:

    1.343     348.222     484844.333
12349.000002   -2.433333

So those wonderful decimals line up. Is there an easy way to do this?

---

you can right-pad like this:

str = '%-10f' % val

to left pad:

set = '%10f' % val

or in combination pad and set the precision to 4 decimal places:

str = '%-10.4f' % val

:

import sys
rows = [[1.343, 348.222, 484844.3333], [12349.000002, -2.43333]]
for row in rows:
  for val in row:
    sys.stdout.write('%20f' % val)
  sys.stdout.write("\n")

        1.343000          348.222000       484844.333300
    12349.000002           -2.433330

---

The % (String formatting) operator is deprecated now.

You can use str.format to do pretty printing in Python.

Something like this might work for you:

for set in temperature_readings:
    for temp in set:
        print "{0:10.4f}\t".format(temp),
    print

Which prints out the following:

    1.3430        348.2220      484844.3333
12349.0000         -2.4333

You can read more about this here: http://docs.python.org/tutorial/inputoutput.html#fancier-output-formatting

---

If you also want to display a fixed number of decimals (which probably makes sense if the numbers are really temperature readings), something like this gives quite nice output:

for line in temperature_readings:
   for value in line:
      print '%10.2f' % value,
   print

Output:

      1.34     348.22  484844.33
  12349.00      -2.43

---

In Python 2.*,

for sublist in temperature_readings:
    for item in sublist:
        print '%15.6f' % item,
    print

emits

       1.343000      348.222000   484844.333300
   12349.000002       -2.433330

for your example. Tweak the lengths and number of decimals as you prefer, of course!