Python Program to Count characters surrounding vowels

Last Updated : 11 Dec, 2020

Given a String, the task is to write a Python program to count those characters which have vowels as their neighbors.

Examples:

Input : test_str = ‘geeksforgeeksforgeeks’
Output : 10
Explanation : g, k, f, r, g, k, f, r, g, k have surrounding vowels.

Input : test_str = ‘geeks’
Output : 2
Explanation : g, k have surrounding vowels.

Method 1 : Using loop

In this, we increment counter while checking previous and successive element for vowels using loop.

Python3

# initializing string 
test_str = 'geeksforgeeksforgeeks'
  
# printing original string 
print("The original string is : " + str(test_str)) 
  
res = 0
vow_list = ['a', 'e', 'i', 'o', 'u'] 
for idx in range(1, len(test_str) - 1): 
  
    # checking for preceding and succeeding element to be vowel 
    if test_str[idx] not in vow_list and (test_str[idx - 1] in vow_list or test_str[idx + 1] in vow_list): 
        res += 1
  
# solving for 1st and last element 
if test_str[0] not in vow_list and test_str[1] in vow_list: 
    res += 1
  
if test_str[-1] not in vow_list and test_str[-2] in vow_list: 
    res += 1
  
# printing result 
print("Characters around vowels count : " + str(res)) 

Output:

The original string is : geeksforgeeksforgeeks

Characters around vowels count : 10

Method 2 : Using sum() and list comprehension

In this, we perform the task of getting count using sum() and iteration and filtering is done using list comprehension.

Python3

# initializing string 
test_str = 'geeksforgeeksforgeeks'
  
# printing original string 
print("The original string is : " + str(test_str)) 
  
vow_list = ['a', 'e', 'i', 'o', 'u'] 
  
# sum() accumulates all vowels surround elements 
res = sum([1 for idx in range(1, len(test_str) - 1) if test_str[idx] 
           not in vow_list and (test_str[idx - 1] in vow_list or test_str[idx + 1] in vow_list)]) 
  
# solving for 1st and last element 
if test_str[0] not in vow_list and test_str[1] in vow_list: 
    res += 1
  
if test_str[-1] not in vow_list and test_str[-2] in vow_list: 
    res += 1
  
# printing result 
print("Characters around vowels count : " + str(res)) 