Ytukyg

For the purpose of this function a valid delimiter is the quotation mark(")or the apostrophe('). Correctly delimited strings must use the same delimiter for the beginning and end character, and that delimiter must not be used within the string. Your function should return the result as a Boolean value.

Here are examples of how your function should work.

test1 = input("Enter a test string: ") #user enters: "hello worlds"

print(valid_string(test1))             #True

It's from my previous test and I received a perfect zero. Can someone show me where to start with?

The key to figuring this out is here:

Correctly delimited strings must use the same delimiter for the beginning and end character, and that delimiter must not be used within the string.

You can check that the string begins with a double quote by doing something like my_string[0] == '"', and similarly for the end by doing my_string[-1] == '"'. This works because string[0] and string [-1] will access the first and last characters, respectively. In case you're not aware, negative indexes in Python just mean to start counting from the end (so index -2 would mean the second from the end, etc).

You can then check that no double-quote occurs inside of the string by doing something like this: my_string[1:-1].count('"') == 0. This works because my_string[1:-1] takes the part of the string excluding the first and last character, and then count hte number of times that the double quote occurs (zero- it should never occur).

But wait! The single quote can also be a delimiter! I'll leave that as a challenge for you. Hint: make sure the starting and ending delimiter are the same, and also make sure to allow the other delimiter to occur inside of the string. You should also think about handling edge cases with strings that are 0 or 1 characters long. Let me know if any parts of this answer don't make sense or if you would like clarification on something.

Ok this should work:

def valid_string(s):

    try:

        return s[0] == s[-1] and s[0] in ["'", '"'] and s[0] not in s[1:-1] and len(s) > 1

    except:

        return False





while True:

    test1 = input("Enter a test string: ")

    print(valid_string(test1))

This works find for strings less that 2 characters long:

$ ./valid_string2.py

Enter a test string: 'adsdasfd"adfadfs'

True

Enter a test string: 'adsfdsafdfs'adsfasd'

False

Enter a test string: "adsfdasf'adsfads"

True

Enter a test string: "adsfasdf"adfasd"

False

Enter a test string: """

False

Enter a test string: "'"

True

Enter a test string: '"'

True

Enter a test string: a

False

Enter a test string: 'a'

True

Enter a test string: "a'

False

Enter a test string: a'

False

Enter a test string: 'a"

False