How can I make a function that prints the number of unique vowels in a string?

Question

I am creating a program that prints the number of unique vowels in a string, whether upper or lower case. For example: "swEet” would print 1. What I have so far prints the number of vowels but not unique ones. What can I change or add to my code to do this? Thank you. I'm a beginner in Python and coding.

import sys

def count_vowels(sys_str):

    sys_str = sys.argv[1].upper()

    vowels = 'aeiou'

    count = len([c for c in sys_str.lower() if c in 
    vowels])

    return count

sys_str = sys.argv[1].upper()
count = count_vowels(sys_str)
print(count)

Source: DBrowne's answer at Counting the number of vowels in a string using for loops in Python I got some of my code from this user in this question.

Answer 1

• First off Eat actually has 2 vowels "E" and "a".

• Second You won't need to use the sys module

• You can simplify your code to this if you're just trying to find the vowels in a string:

  def count_vowels(sys_str):
      vowels = 'aeiou'
      count = len([c for c in sys_str.lower() if c in vowels])
      return count
  

• As for finding unique vowels you can write something like this:

    def count_vowels(string):
        vowels = 'aeiou'
        hashmap = {}
        array = []

        for i, c in enumerate(string.lower()):
            if c not in hashmap:
                array.append(c)
                hashmap[c] = i
            else:
                array.pop(hashmap[c])
        return len(array)

Example:

count_vowels('Eeat')
Output: 1 #<- This is because there are 2 e's now so a is the only unique vowel

• Obviously, there's a lot more efficient time and space solution out there. This is just something off the top of my head. Hopes This helps!

Answer 2

Is there a requirement that you use for loops? The set type is much better suited to this type of problem -- no iteration necessary (at least in Python, there's obviously still iteration on the back end in C).

VOWELS = set("aeiou")


def count_vowels(s: str) -> int:
    return len(VOWELS.intersection(s.lower()))

Examples:

In [6]: count_vowels("Eat")
Out[6]: 2

In [7]: count_vowels("sweEt")
Out[7]: 1

In [8]: count_vowels("hello")
Out[8]: 2

In [9]: count_vowels("aeiou")
Out[9]: 5

In [10]: count_vowels("aeiou"*10)
Out[10]: 5

In [11]: count_vowels("")
Out[11]: 0

In [12]: count_vowels("syzygy")
Out[12]: 0