Question

What I have is a string that looks for example like this {[]}{([])}()and I loop it through to find if it is an open or a close bracket and append it to the list.
What I wanna do now is to find which is the deepest nasting and print it out. So in this example i would print the middle {([ but I am confused how to do it. I can append the beginning of the open brackets and then reset it but how to compare couple of them though, and printing the biggest one

my code:

def is_nested(str):
    stack = []
    deepest =[]
    index=1
    open=0
    for c in str:
        if c == "{" or c == "(" or c == "[" or c =="<":
            stack.append(c) # this is push
            deepest.append(c)
            open +=1
            index +=1
        elif c == "}":
            x = stack.pop()
            index +=1
            if x != "{":
                index -=1
                x2=parens(x)
                return "False: expected %s at character index %d, but received } instead." %(x2,index)
        elif c == "]":
            x = stack.pop()
            index +=1
            if x != "[":
                index -=1
                x2=parens(x)
                return "False: expected %s at character index %d, but received ] instead." %(x2,index)
        elif c == ">":
            x = stack.pop()
            index +=1
            if x != "<":
                index -=1
                x2=parens(x)
                return "False: expected %s at character index %d, but received > instead." %(x2,index)
        elif c == ")":
            x = stack.pop()
            index +=1
            if x != "(":
                index -=1
                x2=parens(x)
                return "False: expected %s at character index %d, but received ) instead." %(x2,index)

    check(str)
    return True
def check(str):
    deepest =[]
    for c in str:
        if c == "{" or c == "(" or c == "[" or c =="<":
            deepest.append(c)
    print deepest


def parens(x):
    if x == "<":
        return ">"
    elif x =="(":
        return ")"
    elif x == "{":
        return "}"
    elif x == "[":
        return "]"


print is_nested("{[()}")
print is_nested("([)")
print is_nested("{[]({})}")
print is_nested("<()>")
print is_nested("{(<)}")

Answer 1

Not sure if I understand your wishes correctly, but this finds the longest sequence of successive opening brackets:

In [20]: import re

In [21]: s = '{[]}{([])}()'

In [22]: max(re.findall("[\(\[\{]+",s),key=len)
Out[22]: '{(['