How to print frequencies in descending order?

Question

I've had a look at other similar questions already but haven't been able to apply the answers to my program. At the moment the frequencies are printed in ascending order, what do I change to make it print it in descending order?

from sys import argv
frequencies = {}
for ch in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ':
   frequencies[ch] = 0

for filename in argv[1:]:
    try:
        f = open(filename)
    except IOError:
        print 'skipping unopenable', filename
        continue

 text = f.read()                
 f.close()                      

 for ch in text:                
     if ch.isalpha():
         ch = ch.upper()
         frequencies[ch] = frequencies[ch] + 1

for ch in 'ABCDEFGHIJKLMNOPQRSTUVWXYZ':
    print ch, frequencies[ch]

Thanks in advance.

You mean descending alphabetical order? or descending frequency order. It looks like you must mean alphabetical. — sblom, May 12 '12 at 06:29

score 5 · Answer 1 · answered May 12 '12 at 06:43

You don't have to reinvent the wheel. Use standard library features:

from sys import argv
from collections import Counter

frequencies = Counter()

for filename in argv[1:]:
    with open(filename) as f:
        text = f.read()
    frequencies.update(ch.upper() for ch in text if ch.isalpha())

for ch, freq in frequencies.most_common():
    print ch, freq

score 2 · Answer 2 · answered May 12 '12 at 06:30

2

You can call items on the dict to get a list of tuples of the items in the dictionary. You can then (reverse) sort by the second item in the tuple (the value in the dict, the frequency):

sorted(frequencies.items(), key=lambda x: -x[1])

By the way, rather than using 'ABCD..., you can use string.ascii_uppercase.

answered May 12 '12 at 06:30

icktoofay

126,289
21
250
231

Thanks but bit confused. Where do I add item and dict? – user1390700 May 12 '12 at 06:35
@user1390700: `frequencies` is a `dict`. `items` is a method on `dict`s. Basically, rather than outputting with `for ch in 'ABC...':` `print ch, frequencies[ch]`, you can use `for ch, freq in sorted(...):` `print ch, freq` – icktoofay May 12 '12 at 06:40
Just wondering if I wanted to change to find the frequencies of words rather than letters what would I change in the coding? – user1390700 May 12 '12 at 08:00
@user1390700: If you used a `Counter` as suggested in [eumiro's answer](http://stackoverflow.com/a/10561660), then you could get a list of words with `text.split()` (although that would include punctuation in the words) or a regular expression like `\w+` (which would not). Then just loop over those words and count as you would the letter. (i.e. `frequencies.update(word)`) – icktoofay May 12 '12 at 19:20
@user1390700: If you don't want to use a `Counter`, then a `defaultdict` might work. If you don't want to use either, then you'd need to check if the word is in the dictionary first, and if it isn't, set it to 1; if it is, increment it. (basically what a `Counter` would do) – icktoofay May 12 '12 at 19:21
Thanks i shall give it a go. Cheers – user1390700 May 13 '12 at 07:55

score 0 · Answer 3 · answered May 12 '12 at 06:27

0

Descending from Z to A? Change the string constant on the second last line to 'ZYXWV...A'.

answered May 12 '12 at 06:27

Antti Huima

25,136
3
52
71

Sorry I mean frequency order. – user1390700 May 12 '12 at 06:30

namit · Answer 4 · 2012-05-12T10:23:01.783

0

from sys import argv
tre="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

for filename in argv[1:]:
    with open(filename) as f:
        text = f.read()
        ttt=list(set(zip(tre,map(text.count,tre))))
        ttt1=sorted([[x[1],x[0]] for x in ttt])
        ttt1.reverse()
        ttt3=[[x[1],x[0]] for x in ttt1]
        for x in ttt3:
            print x[0],x[1]

edited May 12 '12 at 10:23

answered May 12 '12 at 09:19

namit

6,780
4
35
41

How to print frequencies in descending order?

4 Answers4

Linked

Related