NameError: name 'args' is not defined when trying to print out the number of vowels in a string

Question

Create a program called countVowels.py that has a function that takes in a string then prints the number of unique vowels in the string (regardless of it being upper or lower case).

countVowels.py

import sys

def count_vowels(args):
    vowels = set()

    for arg in args:
        for char in arg:
            if char.lower() in 'aeiou':
                vowels.add(char)
    return len(vowels)

print(count_vowels(sys.argv[1:]))

Test Cases

python3 countVowels.py Data
python3 countVowels.py 'Python Python'
python3 countVowels.py 'eiOuayOI j_#Ra'

The following is the error message displayed:

Traceback (most recent call last):
  File "countVowels.py", line 14, in <module>
    count_vowels(args)
NameError: name 'args' is not defined

Answer 1

Right, because it's not defined. You need to pass the sys.argv subset to the function. Right now, you are throwing away the parameter args by overwriting it.

What you should do is delete the sys.argv reference in the function:

def count_vowels(args):
    count = 0 
...

And change the main to:

count_vowels(sys.argv[1:])

Followup

To get the number of UNIQUE vowels, you should collect them all into a set, then count the length of the set.

def count_vowels(args):
    vowels = set() 
    for arg in args:
        for char in arg:
            if char.lower() in 'aeiou':
                vowels.add(char)
    return len(vowels)

print(count_vowels(args))