Python code to count the recurrence of a letter in a word

Question

I need your help to calculate the recurrence of a letter in the word.

Input (string): HelloWorld
Output: H1e1l3o2W1r1d1  

Answer 1

You need a run-length-encoding algorithm on the input.

GeeksforGeeks has a great article on this:

https://www.geeksforgeeks.org/run-length-encoding-python/

# Python code for run length encoding 
from collections import OrderedDict 
def runLengthEncoding(input): 
  
    # Generate ordered dictionary of all lower 
    # case alphabets, its output will be  
    # dict = {'w':0, 'a':0, 'd':0, 'e':0, 'x':0} 
    dict=OrderedDict.fromkeys(input, 0) 
  
    # Now iterate through input string to calculate  
    # frequency of each character, its output will be  
    # dict = {'w':4,'a':3,'d':1,'e':1,'x':6} 
    for ch in input: 
        dict[ch] += 1
  
    # now iterate through dictionary to make  
    # output string from (key,value) pairs 
    output = '' 
    for key,value in dict.items(): 
         output = output + key + str(value) 
    return output 
   
# Driver function 
if __name__ == "__main__": 
    input="wwwwaaadexxxxxx"
    print (runLengthEncoding(input))

Output:

'w4a3d1e1x6'

Your Example:

input = 'hello world'
print(runLengthEncoding(input))

Output:

'h1e1l3o2 1w1r1d1'

Exactly how you wanted it.

Above code from GeeksforGeeks link.

Answer 2

As mentioned by others, you can use str.count(). One easy approach is to look at the first letter, count it, then delete all instances of it from the string and repeat. A simple recursive answer might look like:

def count(word):
    if len(word) == 0:
        return ""
    return word[0]+str(word.count(word[0]))+count(word[1:].replace(word[0], ""))

Answer 3

use string.count() .

The syntax is as follows:

string.count(substring, [start_index],[end_index])

substring is the letter you are trying to find, [start_index] is the letter at which to start searching (remember, python starts at 0 when using indexes) and [end_index] is at which letter to stop searching.

Answer 4

I think this function should do the trick:

def countoccurences(word, character):
    occuresin =[]
    for letter in word:
        if letter == character:
            occuresin.append(letter)
        
    print("Letter", character, " occurs in string: ", str(len(occuresin)), " times.")
    return len(occuresin)

countoccurences("1se3sr4g45h7e5q3e", 'e')