Python for loop iterating an already iterated item

Question

So I was trying to solve this leetcode problem:

Input: command = "G()(al)"

Output: "Goal"

Explanation: The Goal Parser interprets the command as follows:

G -> G

() -> o

(al) -> al

The final concatenated result is "Goal".

This is my code:

def interpret(command: str) -> str:
        
        res = ''
        
        for i in command:
            
            if i == 'G':
                res += i
            
            if i == '(':
                ind = command.index(i)
                if command[ind + 1] == ')':
                    res += 'o'
                if command[ind + 1] == 'a':
                    res += 'al'
        
        return res

The problem is, instead of returning 'Goal', the function returns 'Goo'. So I changed the function to the following to see what's going on:

for i in command:
            if i == '(':
                print(command.index(i))

And the above code prints out this

1
1

which means the loop is iterating an element twice?

What did I do wrong and how can I fix the function to return the correct output?

Stefano Gallotti · Accepted Answer · 2020-12-10 04:49:24Z

3

command.index() gives you the first occurrence of '('.

Rewrite your function as follows:

def interpret(command: str) -> str:

    res = ""

    for c, i in enumerate(command):

        if i == "G":
            res += i

        if i == "(":
            ind = c
            if command[ind + 1] == ")":
                res += "o"
            if command[ind + 1] == "a":
                res += "al"

    return res

answered Dec 10, 2020 at 4:49

Stefano Gallotti

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2 Comments

ShadowRanger Over a year ago

Note: It's really weird to name the index c and the value i; i is almost always the name of the index. I realize the OP used i for the value, but ugh, don't encourage that.

v1ct0rv00rh33s Over a year ago

Ohhh now that makes perfect sense! Thanks mate

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