issue iterating a python string list-CodePudding

Hello I'm getting an issue while I'm trying to remove every len of string in the list that is mod by 2

def remove_even_length(l):
for i in l:
    if  len(i) %2==0:
        if i in l:

            l.remove(i)


return l

wordlist = ["be", "is", "not", "or", "question", "the", "to"] print(remove_even_length(wordlist))

what is happening is when it goes inside the list it skips ,[is , question] which both are mod 2 I don't know why it doesn't check the len of these 2 strings.

CodePudding user response：

Might be a problem resulting from the fact that you are iterating over the list while changing it.

Try creating a new list and returning it:

def remove_even_length(old_list):
    new_list = []
    for i in old_list:
        if len(i) % 2 != 0:
            new_list.append(i)
    return new_list


wordlist = ["be", "is", "not", "or", "question", "the", "to"]
wordlist_without_even = remove_even_length(wordlist)
print(wordlist_without_even)

Or just use a List Comprehension:

wordlist = ["be", "is", "not", "or", "question", "the", "to"]
wordlist_without_even = list([word for word in wordlist if len(word) % 2 != 0])
print(wordlist_without_even)

CodePudding user response：

You're operating on the list as you're iterating through it. Try creating a separate results list, and pushing the values that do/don't fit your criteria to this new list. I think you'll find your results then.

CodePudding user response：

It happens because you are removing elements while iterating which changes the length of list while looping. You can use the following code to remove the elements based on a condition in one line.

def remove_even_length(l):
    l1 = [x for x in l if len(x) % 2]


    return l1

CodePudding user response：

I figure it out I must remove every even element backwards.

def remove_even_length(l):
for i in l[::-1]:
    if not (len(i) %2==1):
        l.remove(i)
return l
wordlist = ["be", "is", "not", "or", "question", "the", "to"]
print(remove_even_length(wordlist))