[Tut] How to Count Vowels in a String

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How to Count Vowels in a String

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Problem Formulation and Solution Overview

In this article, you’ll learn how to count the number of vowels in a string.

To make it more fun, we have the following running scenario:

In Canada, we have a province called Saskatchewan. This province has a large amount of flat land. In this article, we reference their local saying.

Question: How would we write Python code to count the vowels in a String?

We can accomplish this task by one of the following options:

• Method 1: Use Regex and Dictionary Comprehension
  
  
• Method 2: Use List Comprehension and
  Code:

  count()
  
  
  
• Method 3: Use
  Code:

  Counter()
  and
  Code:

  count.update()
  
  
  
• Method 4: Use
  Code:

  for
  and
  Code:

  count()
  
  
  
• Method 5: Use
  Code:

  map()
  and
  Code:

  count()
  
  

Add the following code to the top of each code snippet. This snippet will allow the code in this article to run error-free.

Code:

import re from collections import Counter

Method 1: Use Regex and Dictionary Comprehension

This example uses

Code:

Regex

and

Code:

Dictionary Comprehension

as a one-liner to tally the number of specified vowels in a string. The results return in a Dictionary format.

Code:

saying = 'Saskatchewan! Where you can watch your dog run away for 3 days.' vcount = {x: len(re.findall(f"{x}", saying.lower())) for x in 'aeiou'} print(vcount)

A Finxter Favorite!

This code declares the string

Code:

saying

. Then, https://blog.finxter.com/list-comprehension/Dictionary Comprehension converts the string to lowercase and

Code:

re.findall()

searches for and tallies each specified vowel.

The results save to

Code:

vcount

and are output to the terminal.



Output

Code:

{'a': 8, 'e': 3, 'i': 0, 'o': 4, 'u': 3}

Method 2: Use List Comprehension and count()

This example uses List Comprehension to tally the number of specified vowels in a string. The results return in a List format.

Code:

saying = 'Saskatchewan! Where you can watch your dog run away for 3 days.' vcount = [saying.lower().count(x) for x in 'aeiou'] print(vcount)

This code declares the string

Code:

saying

. Then, List Comprehension converts the string to lowercase and searches for and tallies each specified vowel.

The results save to variable

Code:

vcount

and are output to the terminal.



Output

Code:

[8, 3, 0, 4, 3]

Note: This output displays the totals but not their associated vowel.

Method 3: Use Counter() and count.update()

This example calls the Collections library and uses

Code:

Counter()

to count the number of specified vowels in a string.

Code:

saying = 'Saskatchewan! Where you can watch your dog run away for 3 days.' count = Counter() for i in saying: if i in 'aeiou': count.update(i.lower()) print(dict(count))

This code declares the string

Code:

saying

and initiates the

Code:

Counter()

object,

Code:

count

.

A

Code:

for

loop instantiates and traverses through each character converting to lowercase, searching for and tallies each specified vowel.

The results save to

Code:

count

and are output to the terminal.

If this code was output to the terminal using

Code:

print(count)

, the output would be as follows:

Output using

Code:

print(count)

Code:

Counter({'a': 8, 'o': 4, 'e': 3, 'u': 3})

Placing

Code:

count

inside

Code:

dict()

removes the word

Code:

Counter

and surrounding braces

Code:

()

.

Output using

Code:

print(dict(count))

Code:

{'a': 8, 'e': 3, 'i': 0, 'o': 4, 'u': 3}

Note: This method produces the same output as Method 1 but with four (4) additional lines of code.

Method 4: Use For and count()

This example uses a

Code:

for

loop and

Code:

string.count()

to tally the number of specified vowels in a string. The results return as a string.

Code:

saying = 'Saskatchewan! Where you can watch your dog run away for 3 days.' tmp = '' for i in 'aeiou': tmp += i + ':' + str(saying.count(i)) + ' ' print(tmp)

This code declares the string

Code:

saying

and initiates a variable

Code:

tmp

.

A

Code:

for

loop instantiates and traverses through each character, searching for and tallying each specified vowel. The results convert to a string, save to

Code:

tmp

, and are output to the terminal.

Output

Code:

a:8 e:3 i:0 o:4 u:3

Method 5: Use map() and count()

This example uses

Code:

map()

and

Code:

count()

to tally the number of specified vowels in a string.

Code:

saying = 'Saskatchewan! Where you can watch your dog run away for 3 days.' print(*map(saying.lower().count, 'aeiou'))

This code declares the string,

Code:

saying

converts the string to lowercase, and tallies the specified vowel. The results are output to the terminal.



Output

Code:

8 3 0 4 3

Summary

In this case,

Code:

lower()

was not required as you could see no vowels were in uppercase. However, you may not always know what a string will contain. In this case, best to convert to either lowercase or uppercase.

These five (5) methods of counting vowels in a string should give you enough information to select the best one for your coding requirements.

Good Luck & Happy Coding!