change_case

snippets/count_vowels.md

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+### count_vowels
+
+Retuns `number` of vowels in provided `string`.
+
+Use a regular expression to count the number of vowels `(A, E, I, O, U)` in a string.
+
+```python 
+import re
+
+
+def count_vowels(str):
+    return len(len(re.findall(r'[aeiou]', str, re.IGNORECASE)))
+
+```
+
+``` python
+count_vowels('foobar') # 3
+count_vowels('gym') # 0
+```