Mapping and Filtering Help for Lists

[Zethex]

Alright I got asked today by a friend this question, which obviously I
couldn't help him with.

He needs to get rid of words in a string referring to an already given list
then needs to map them using a function he already has. Ill explain this
better by giving an example :P

Say ur given these lists:

un_words = ['a', 'the', 'he', 'she', 'uses', 'with']
alterns = [ ['book', 'textbook', 'notepad'], ['pencil', 'pen', 'pacer'] ]

The problem asks to create a "compareandremove" so that you can use it on a
string, to remove the words from the string that are contained in un_words.

The remaining words then need to be compared to the alterns list and either
bring back the word if no matches or bring back the list. To better explain
that i'll use an example.

If i do compareandremove('notepad a pencil with desk')

I need it so it removes words contained in un_words, so "a" and "with";
then compares the remaining words to alterns to find a match.

This should bring back:

['notepad', 'book', 'textbook', 'pencil', 'pen', 'pacer', 'desk']
Any tips on how to create this function or maybe the function itself so I
can then show him how to do it.

Thank you.
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[Arnaud Delobelle]

Zethex <ze****@hotmail.comwrites:

Alright I got asked today by a friend this question, which obviously I
couldn't help him with.

He needs to get rid of words in a string referring to an already given list
then needs to map them using a function he already has. Ill explain this
better by giving an example :P

Say ur given these lists:

un_words = ['a', 'the', 'he', 'she', 'uses', 'with']
alterns = [ ['book', 'textbook', 'notepad'], ['pencil', 'pen', 'pacer'] ]

The problem asks to create a "compareandremove" so that you can use it on a
string, to remove the words from the string that are contained in un_words.

The remaining words then need to be compared to the alterns list and either
bring back the word if no matches or bring back the list. To better explain
that i'll use an example.

If i do compareandremove('notepad a pencil with desk')

I need it so it removes words contained in un_words, so "a" and "with";
then compares the remaining words to alterns to find a match.

This should bring back:

['notepad', 'book', 'textbook', 'pencil', 'pen', 'pacer', 'desk']
Any tips on how to create this function or maybe the function itself so I
can then show him how to do it.

Thank you.

Look away now if you don't want a complete solution!

un_words = ['a', 'the', 'he', 'she', 'uses', 'with']
alterns = [ ['book', 'textbook', 'notepad'], ['pencil', 'pen', 'pacer'] ]

# these words will be replaced with nothing
wordmap = dict((w, []) for w in un_words)

# these words will be replaced with the list of their synonyms
for wordlist in alterns:
for word in wordlist:
wordmap[word] = wordlist

def compareandremove(sentence):
return [x for w in sentence.split() for x in wordmap.get(w, [w])]
# Example

>>compareandremove('notepad a pencil with desk')

['book', 'textbook', 'notepad', 'pencil', 'pen', 'pacer', 'desk']

--
Arnaud

[Zethex]

Thank you a lot!

Another quick couple of questions.

How can i make it so it removes special operators such as ? ! or doesnt
include them?

and

I need to lowercase the words so should i use sentence = sentence.lower()?
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[Arnaud Delobelle]

Zethex <ze****@hotmail.comwrites:

Thank you a lot!

Another quick couple of questions.

How can i make it so it removes special operators such as ? ! or doesnt
include them?

As you are doing lots of string manipulations, I advise you to read
the section of the python documentation on strings (link below). This
way you will get a good idea of what can be done out of the box with
strings in python.

http://docs.python.org/lib/string-methods.html

(Or type help(str) from the interactive prompt)

For the particular task of removing a character, you may be interested
in the replace() method.

and

I need to lowercase the words so should i use sentence = sentence.lower()?

Yes.

Or you could combine the two by using the translate() method. E.g.

>>table = ''.join(chr(c).lower() for c in range(256))
'You! are Free??'.translate(table, '!?')

'you are free'

HTH

--
Arnaud