title: how to get a function to read input and define it
body: <p>I'm trying to make code that allows me to take an input string and return how many vowels are in that input string. I had it working with built in functions, but my teacher asked me to then convert it to a user defined function and I've been having a ton of problems. I managed to fix most of them, and have spent several hours trying to search for the answer but I don't know enough terminology yet to search well.</p>
  
  <p>I've tried(and have been fiddling with it for a couple of hours now but no luck.):</p>
  
  <pre><code>def count_vowels(string):
      string = input('Enter string: ')
  
  def count_vowels(i):
      return i in string
      if(i=='a' or i=='e' or i=='i' or i=='o' or i=='u' or i=='A' or i=='E' or i=='I' or i=='O' or i=='U' ):
          vowels = vowels + 1
  
  print(count_vowels(string))
  </code></pre>
  
  <p>Current error is 'i' is undefined.</p>