Character Distribution (Level II)

The purpose of this challenge is to gain proficiency with looping, decision making and lists.

Write and submit a Python program distribution.py that computes and displays the distribution of characters in a given sample of text.

Output of your program should look like this:

Please enter a string of text (the bigger the better): The rain in Spain stays mainly in the plain.
The distribution of characters in "The rain in Spain stays mainly in the plain." is:
iiiiii
nnnnnn
aaaaa
sss
ttt
ee
hh
ll
pp
yy
m
r

Notice about this example:

• The text: The rain ... plain is provided by the user as input to your program.
• Uppercase characters are converted to lowercase
• Spaces and punctuation marks are ignored completely.
• Characters that are more common appear first in the list.
• Where the same number of characters occur, the lines are ordered alphabetically. For example, in the printout above, the letters e, h, l, p and y both occur twice in the text and they are listed in the output in alphabetical order.
• Letters that do not occur in the text are not listed in the output at all.

There are a few techniques or tricks that you may find handy when working on this challenge. If you see something here that sounds useful, feel free to learn more about it!

• The code: 'a string has several characters'.count('a') will return 5, which is the number of times the character 'a' appears in the string.
• The code: zip([1,4,2],['a','z','q']) will return an iterator for generating a list of tuples (another type of list) like this: [(1, 'a'), (4, 'z'), (2, 'q')].
• If mylist is a list like [435, 2, 45, 2] then mylist.sort() will change it to: [2, 2, 45, 435].
• If mylist is a list like [435, 2, 45, 2] then mylist.append(99) will change it to: [435, 2, 45, 2, 99].
• If mylist is a list like [435, 2, 45, 2] then mylist[-1] will return 2, the last element in the list.
• You can get the length of a string, or number of elements in a list using the builtin len() function. For example: len([435, 2, 45, 2]) will return 4.
• If you import string then use string.ascii_lowercase to get a string with the letters a-z in it.