Python: Count the number of occurrence of a specific character in a string

Last update on December 21 2024 09:12:53 (UTC/GMT +8 hours)

Character Frequency Counter

Write a Python program to count the number of occurrences of a specific character in a string.

Pictorial Presentation:

Sample Solution:

Using count() function:

Python Code:

# Create a string 's' containing a sentence.
s = "The quick brown fox jumps over the lazy dog."

# Print a message indicating the original string.
print("Original string:")

# Print the original string 's'.
print(s)

# Print a message indicating the number of occurrences of 'o' in the string.
print("Number of occurrences of 'o' in the said string:")

# Print the count of occurrences of the character 'o' in the string 's'.
print(s.count("o"))

Sample Output:

Original string:
The quick brown fox jumps over the lazy dog.
Number of occurrence of 'o' in the said string:
4

Using loop:

Python Code:

# Create a string 's' containing a sentence.
s = "The quick brown fox jumps over the lazy dog."

# Print a message indicating the original string.
print("Original string:")

# Print the original string 's'.
print(s)

# Print a message indicating the number of occurrences of 'o' in the string.
print("Number of occurrences of 'o' in the said string:")

# Initialize a counter variable 'ctr' to 0.
ctr = 0

# Iterate through each character 'c' in the string 's'.
for c in s:
    # Check if the character 'c' is equal to 'o'.
    if c == 'o':
        # If 'c' is 'o', increment the counter 'ctr' by 1.
        ctr = ctr + 1

# Print the final count of occurrences of 'o' in the string 's'.
print(ctr)

Sample Output:

Original string:
The quick brown fox jumps over the lazy dog.
Number of occurrence of 'o' in the said string:
4

Flowchart:

Using collections.Counter():

Python Code:

# Import the Counter class from the collections module.
from collections import Counter

# Create a string 's' containing a sentence.
s = "The quick brown fox jumps over the lazy dog."

# Print a message indicating the original string.
print("Original string:")

# Print the original string 's'.
print(s)

# Print a message indicating the number of occurrences of 'o' in the string.
print("Number of occurrences of 'o' in the said string:")

# Use the Counter class to count the occurrences of characters in the string 's'.
ctr = Counter(s)

# Print the count of the character 'o' from the Counter.
print(str(ctr['o']))

Sample Output:

Original string:
The quick brown fox jumps over the lazy dog.
Number of occurrence of 'o' in the said string:
4

Using Lambda functions:

Python Code:

# Create a string 's' containing a sentence.
s = "The quick brown fox jumps over the lazy dog."

# Print a message indicating the original string.
print("Original string:")

# Print the original string 's'.
print(s)

# Print a message indicating the number of occurrences of 'o' in the string.
print("Number of occurrences of 'o' in the said string:")

# Use the `map` function along with a lambda function to count occurrences of 'o' in the string 's'.
# It maps '1' for each character containing 'o' and '0' otherwise and then sums those values.
ctr = sum(map(lambda x: 1 if 'o' in x else 0, s))

# Print the count of occurrences of 'o'.
print(ctr) 

Sample Output:

Original string:
The quick brown fox jumps over the lazy dog.
Number of occurrence of 'o' in the said string:
4

Using Regular Expressions:

Python Code:

# Import the 're' module, which provides support for regular expressions.
import re

# Create a string 's' containing a sentence.
s = "The quick brown fox jumps over the lazy dog."

# Print a message indicating the original string.
print("Original string:")

# Print the original string 's'.
print(s)

# Print a message indicating the number of occurrences of 'o' in the string.
print("Number of occurrences of 'o' in the said string:")

# Use the 're.findall' function to find all occurrences of 'o' in the string 's' and then count them.
ctr = len(re.findall("o", s))

# Print the count of occurrences of 'o'.
print(ctr)

Sample Output:

Original string:
The quick brown fox jumps over the lazy dog.
Number of occurrence of 'o' in the said string:
4

Python Code Editor:

Previous: Write a Python program to test if a certain number is greater than all numbers of a list.
Next: Write a Python program to check if a file path is a file or a directory.