Function that is made to remove round brackets does not work, Python 3-CodePudding

I have a function that takes in an argument, preferably a string, takes each value of the string and implements them as elements in a list. After that, it iterate's through the list and is supposed to delete/remove elements that are round brackets, so basically, these: ( ). Here is the code:

def func(s):
    n = 0
    s = [i for i in s]
    for i in s:
        if s[n] == "(" or s[n] == ")":
            del s[n]
        else:
            n  = 1
            continue
    return s
print(func("ubib0_)IUBi(biub()()()9uibib()((U*H)9g)*(GB(uG(*UV(V79V*&^&87vyutgivugyrxerdtufcviO)()(()()()(0()90Y*(g780(&*^(UV(08U970u9yUV())))))))))"))

However, the function stops the iteration and ends/returns the list early (when some round brackets are still there).

I also went with another way, a way that works:

def func(s):
    n = 0
    s = [i for i in s]
    s2 = [i for i in s if i != "(" and i != ")"]
    return s2
print(func("ubib0_)IUBi(biub()()()9uibib()((U*H)9g)*(GB(uG(*UV(V79V*&^&87vyutgivugyrxerdtufcviO)()(()()()(0()90Y*(g780(&*^(UV(08U970u9yUV())))))))))"))

Why does this work while the other way doesn't? They like they'd output the same result. What am I doing wrong in the first example?

CodePudding user response：

Your concept is correct, in that you either delete the current item or increment n.

Where you've gone wrong is that you're iterating over each letter which doesn't make sense given the above info. Changing for i in s to while n < len(s) will fix the problem.

A couple of things you may find useful:

list(s) looks cleaner than [i for i in s]
i not in "()" is another way to write i != "(" and i != ")"

CodePudding user response：

At the beginning when you're increasing n, n equals to i. But when you meet a bracket, n has the same value the next iteration, and i increases. It happens every time s[n] == "(" or s[n] == ")" and the difference between n's and i's values increases.

To work correctly you program needs to check every symbol in the list (string) for equality of either '(' or ')' using s[n], but it doesn't happen because the iteration stops when i achieves the end of the list and n at that time is much less than i and it hasn't achieved the end of the list yet and hasn't checked all symbols.