Write a sort function for a list of 4 -tuples.
Below is a list of the nearest stars and some of their properties. The list
elements are 4 -tuples containing the name of the star, the distance from the
sun in light years, the apparent brightness, and the luminosity. The apparent
brightness is how bright the stars look in our sky compared to the brightness
of Sirius A. The luminosity, or the true brightness, is how bright the stars
would look if all were at the same distance compared to the Sun. The list data
are found in the file stars. list, which looks as follows:
The purpose of this exercise is to sort this list with respect to distance,
apparent brightness, and luminosity.
To sort a list data, one can call sorted(data), which returns the sorted list
(cf. Table 2.1). However, in the present case each element is a 4 -tuple, and
the default sorting of such 4 -tuples result in a list with the stars
appearing in alphabethic order. We need to sort with respect to the 2nd, 3rd,
or 4th element of each 4 -tuple. If a tailored sort mechanism is necessary, we
can provide our own sort function as a second argument to sorted, as in
sorted(data, mysort). Such a tailored sort function mysort must take two
arguments, say a and b, and returns \(-1\) if a should become before
\(\mathrm{b}\) in the sorted sequence, 1 if \(\mathrm{b}\) should become before a,
and 0 if they are equal. In the present case, a and \(b\) are 4-tuples, so we
need to make the comparison between the right elements in a and b. For
example, to sort with respect to luminosity we write
def mysort \((a, b):\)
if \(a[3]b[3]:\)
return 1
else:
return 0
Write the complete program which initializes the data and writes out three
sorted tables: star name versus distance, star name versus apparent
brightness, and star name versus luminosity. Name of program file:
sorted_stars_data.py.
