2

I have a list of words like the following:

old_list = ['houses','babies','cars','apples']

The output I need is:

new_list = ['house','baby','car','apple']

In order to do this, I came up with a loop:

new_list1 = []
new_list2 = []
for word in old_list:
    if word.endswith("ies"):
        new_list1[:0] = [word.replace("ies","y")] 
    elif word.endswith("s"):
        new_list2[:0] = [word.replace(' ','')[:-1]]

new_list = new_list1 + new_list2 # Order doesn't matter, but len(new_list) == len(old_list)

It's simply not working. I'm getting something like:

new_list = ['baby','house','babie','car','apple']

I'm sure I'm just doing one simple thing wrong but I can't see it. And I would use list.append() if there's an easy way to implement it.

Thanks!

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5
  • 2
    I'm getting ['baby', 'apple', 'car', 'house'] with your code. Commented Oct 8, 2013 at 10:36
  • even i am getting same answer as @Bogdan ...and remove that space between new_list and 2!! Commented Oct 8, 2013 at 10:38
  • I'm checking my code again, I didn't realize that the mistake may be coming from something else. Sorry. Commented Oct 8, 2013 at 10:45
  • @Bogdan: I have a question though, how would you remove any words containing anything else than letters and dashes? Commented Oct 8, 2013 at 10:49
  • @marc, remove from where? I guess something along the lines of [s for s in l if re.match(r'[\-\w]*$', s)] (or with an analogous filter). Commented Oct 8, 2013 at 11:01

6 Answers 6

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6

Firstly, word.replace("ies","y") is not a very good idea; sometimes you can find it in the middle of the word e.g. diesel 

new_list = []
for word in old_list:
    if word.endswith("s"):
        if word.endswith("ies"):
            new_list.append(word[:-3] + "y")
        else:
            new_list.append(word[:-1])
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3 Comments

You hit the nail on the head. The issue is that I needed to check for s first.
How would you then replace all words containing "degree" (ie. "50-degrees" with the word "degree"? I tried new_list.append("degree"), but it still returns the whole word.
Sorry I am not sure I understand. If the old_list contains 50-degrees, the new one will contain 50-degree. If you need to remove 50-, then you need to formalize the rule, e.g. remove evertyhing before -.
5

This doesn't directly address your question (why your attempted code doesn't work as expected) but I suggest to not use a loop in the first place - instead, have a dedicated function for giving the singular form of a given english word, like:

def singular(word):
  # ...
  return singularForm

And then use a list comprehension

new_list = [singular(word) for word in old_list]

It's shorter and IMHO nicely communicates what you do: getting the singular form of every word in old_list instead of talking about how it's done (by looping over the list).

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4

And I would use list.append() if there's an easy way to implement it.

I think you're misunderstanding how list.append() works. Remember that lists are mutable, so you don't need to do the new_list1[:0] = blah. You can just do:

new_list = []
for word in old_list:
    if word.endswith("ies"):
        new_list.append(word.replace("ies","y"))
    elif word.endswith("s"):
        new_list.append(word.replace(' ',''))

Also I'm not seeing what your second replace function should be. If you want to get rid of the 's' (for words such as 'houses'), you can use slicing:

>>> print 'houses'[:-1]
house
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7 Comments

slicing won't turn babies into baby.
@FrerichRaabe I showed the slicing for the second replace. It's not intended for the -ies words
Ah sorry, I thought "second replace" would be the one you're not addressing with your slicing remark.
@FrerichRaabe I clarified it a bit :)
I believe he wanted to remove trailing spaces at the end of word and then to get rid of the s. Something like print 'houses '[:-1] -> house. If I'm right, it may me better written using strip: word.strip()[:-1]
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0

You can do this easily in one line.

new_list = [word[:-1].replace('ie','y') for word in old_list]

Just be careful of words like 'pies' because the code will turn it into 'py'. Maybe that is Python trying to send us secret messages. ;)

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0 
#Use list comprehension to less code#
old_list = ['houses','babies','cars','apples']
new_list = ['house','baby','car','apple']
new_list+=[word.replace('ies','y') for word in old_list if word.endswith('ies')]
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1 Comment

-1 Just dumping a snippet of code without any further explanation is not very educational.
0 
old_list = ['cars', 'babies', 'computers', 'words']

def remove_s_ies(string):
    if string.endswith('ies'):
        return string[:-3]+'y'
    elif string.endswith('s'):
        return string[:-1]


new_words = [ remove_s_ies(word) for word in old_list ]
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