Discussion on: Secret Message

[Talha]

    def give_me_word(text):
        ans=dict()
        the_text=""
        for i in text:
            if i in ans:
                ans[i]+=1
            else:
                ans[i]=1

        comparison=ans['_']
        sorted_list=sorted(ans.values(),reverse=True)
        rev_dict = dict((v,k) for k,v in ans.iteritems())

        for i in sorted_list:
            if(i>=comparison and rev_dict[i]!='_'):
                the_text=the_text+rev_dict[i]
            elif rev_dict[i]=='_':
                break

        return the_text

    text="the_text"

    print give_me_word(text)

Not fully optimized script to do the same in python

[Ben Greenberg]

Python is on my list of things to learn soon and can't help but remark how much it "looks" like Ruby without knowing much about it yet.

[Talha]

"...without knowing much about it yet." This is great about python. Nice challenge this one. :-)

[Ryan Palo]

Nice! Thanks for sharing. :) Have you seen the built-in Counter class? This seems like a perfect use-case for it.

from collections import Counter

blob = "..."
letters = "abcdefghijklmnopqrstuvwxyz_"

def message(letters, blob):
    hist = Counter(blob)    # Counter takes any iterable and makes
                            # a histogram of its items!

    sorted_letters = ''.join(x[0] for x in hist.most_common())
    return sorted_letters.split('_')[0]

print(message(letters, blob))

[edh_developer]

I wondered if I could do better performance-wise, based on knowledge of the problem that the more general built-in classes couldn't take advantage of. Ended up with this:

import string

longString="..."

def decode(msg):
    # Testing suggests this is a little faster than using defaultdict
    charCountHash = {}.fromkeys(string.ascii_lowercase,0)
    charCountHash['_'] = 0

    for ch in msg:
        charCountHash[ch] += 1

    c = charCountHash['_']
    resultHash = {charCountHash[k]: k for k in charCountHash.keys() \
        if charCountHash[k] > c }

    return ''.join( [ resultHash[index] for index in \
        sorted(resultHash.keys(), reverse=True) ] )

print(decode(longString))

Testing both implementations a few times suggests this way is faster, but only 1% or so.

Might try this in go, just for the practice...

[Ryan Palo]

Nice! I haven't used fromkeys before. That's a nice alternative to defaultdict (and you don't have to import anything!) if you already know the keys you need.

[Ryan Palo]

Bonus! On my machine, this version is even 5 times faster than the best Ruby version!

cat test.py | python -m timeit
100000000 loops, best of 3: 0.00844 usec per loop

[Talha]

This is great. Will use counter effectively. Thanks for showing me counter(). :-)