Algo to check that a string doesn't have missing close quote ( ', " OR ` )

Question

What is the best way to check in python that given a string, there are no open quotes in it?

e.g.

// missing quote
bar, fun("foo"), "zaa 

// OK quote
bar, fun("foo), "zaa 

// missing quote
bar, fun("foo), zaa 


// ok quote (single quote encompasses both ends)
bar', fun("foo), zaa' 


// ok quote since there is the escape
bar', \'fun("foo), zaa' 

// missing quote since there is the escape
bar', \'fun("foo), zaa 

// missing quote
bar', fun("foo"), zaa 

I was trying to run something like

regexp(raw, '"(^".*?)"', my_string)
regexp(raw, '`(^`.*?)`', my_string)
regexp(raw, '\'(^\'.*?)\'', my_string)

but this detects only if the string was correctly closed

This was another attempt, but I'm still trying to come up with a clear logic to detect that all of the previous quotes were already closed

regexp(raw, '"(^".*?)$', my_string)

Answer 1

You may not use regex, just use stack to check it. This problem is sort of correct bracket checking problem.

UPD: update quote characters

UPD2: regex is not a perfect tool for this case.

def is_quote_ok(s):
    stack = []
    for c in s:
        if c in ["'", '"', "`"]:
            if stack and stack[-1] == c:
                # this single-quote is close character
                stack.pop()
            else:
                # a new quote started
                stack.append(c)
        else:
            # ignore it
            pass

    return len(stack) == 0

Answer 2

Let's break this problem down:

(1) There is always only one "open" quote.

(2) At the end of the string there must be no open quote.

(3) A quote-symbol that follows the escape-symbol does not open or close a quote.

Solution:

• Create a variable that saves what kind of quote is currently opened and initialize it with the empty string
• Iterate over the letters
• If there is an escape-symbol, skip the next letter
• If there is quote symbol and currently_open is the empty string, change currently_open to the quote symbol
• If there is a quote symbol and currently_open matches the quote-symbol, change currently_open to the empty string
• If there is a quote symbol and currently_open contains another kind of quoute-symbol, do nothing
• If at the end of the string currently_open matches the empty string, answer with true, else with false

That's it, have fun.