How to find index of an element in Python list?

Question

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How to find positions of the list maximum?

A question from homework: Define a function censor(words,nasty) that takes a list of words, and replaces all the words appearing in nasty with the word CENSORED, and returns the censored list of words.

>>> censor([’it’,’is’,’raining’], [’raining’])
[’it’,’is’,’CENSORED’]

I see solution like this:

1. find an index of nasty
2. replace words matching that index with "CENSORED"

but i get stuck on finding the index..

Answer 1

You can find the index of any element of a list by using the .index method.

>>> l=['a','b','c']
>>> l.index('b')
1

Answer 2

Your approach might work, but it’s unnecessarily complicated.

Python allows a very simple syntax to check whether something is contained in a list:

censor = [ 'bugger', 'nickle' ]
word = 'bugger'
if word in censor: print 'CENSORED'

With that approach, simply walk over your list of words and test for each words whether it’s in the censor list.

To walk over your list of words, you can use the for loop. Since you might need to modify the current word, use an index, like so:

for index in len(words)):
   print index, words[index]

Now all you need to do is put the two code fragments together.

Answer 3

Actually you don't have to operate with indexes here. Just iterate over words list and check if the word is listed in nasty. If it is append 'CENSORED' to the result list, else append the word itself.

Or you can involve list comprehension and conditional expression to get more elegant version:

Answer 4

You could use the handy built-in enumerate() function to step through the items in the list. For example:

def censor(words, nasty):
    for i,word in enumerate(words):
       if word...