Run Length Encoding in Python

Read

Courses

Practice

Given an input string, write a function that returns the Run Length Encoded string for the input string. For example, if the input string is ‘wwwwaaadexxxxxx’, then the function should return ‘w4a3d1e1x6’.

Examples:

Input  :  str = 'wwwwaaadexxxxxx'
Output : 'w4a3d1e1x6'

This problem has existing solution please refer Run Length Encoding link. Here we will solve this problem quickly in python using OrderedDict. Approach is very simple, first we create a ordered dictionary which contains characters of input string as key and 0 as their default value, now we run a loop to count frequency of each character and will map it to it’s corresponding key.

Implementation:

Python3

<div id="highlighter_850800" class="syntaxhighlighter nogutter  "><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td class="code"><div class="container"><div class="line number1 index0 alt2"><code class="comments"># Python code for run length encoding</code></div><div class="line number2 index1 alt1"><code class="keyword">from</code> <code class="plain">collections </code><code class="keyword">import</code> <code class="plain">OrderedDict</code></div><div class="line number3 index2 alt2"><code class="keyword">def</code> <code class="plain">runLengthEncoding(</code><code class="functions">input</code><code class="plain">):</code></div><div class="line number4 index3 alt1"> </div><div class="line number5 index4 alt2"><code class="undefined spaces">    </code><code class="comments"># Generate ordered dictionary of all lower</code></div><div class="line number6 index5 alt1"><code class="undefined spaces">    </code><code class="comments"># case alphabets, its output will be</code></div><div class="line number7 index6 alt2"><code class="undefined spaces">    </code><code class="comments"># dict = {'w':0, 'a':0, 'd':0, 'e':0, 'x':0}</code></div><div class="line number8 index7 alt1"><code class="undefined spaces">    </code><code class="functions">dict</code><code class="keyword">=</code><code class="plain">OrderedDict.fromkeys(</code><code class="functions">input</code><code class="plain">, </code><code class="value">0</code><code class="plain">)</code></div><div class="line number9 index8 alt2"> </div><div class="line number10 index9 alt1"><code class="undefined spaces">    </code><code class="comments"># Now iterate through input string to calculate</code></div><div class="line number11 index10 alt2"><code class="undefined spaces">    </code><code class="comments"># frequency of each character, its output will be</code></div><div class="line number12 index11 alt1"><code class="undefined spaces">    </code><code class="comments"># dict = {'w':4,'a':3,'d':1,'e':1,'x':6}</code></div><div class="line number13 index12 alt2"><code class="undefined spaces">    </code><code class="keyword">for</code> <code class="plain">ch </code><code class="keyword">in</code> <code class="functions">input</code><code class="plain">:</code></div><div class="line number14 index13 alt1"><code class="undefined spaces">        </code><code class="functions">dict</code><code class="plain">[ch] </code><code class="keyword">+</code><code class="keyword">=</code> <code class="value">1</code></div><div class="line number15 index14 alt2"> </div><div class="line number16 index15 alt1"><code class="undefined spaces">    </code><code class="comments"># now iterate through dictionary to make</code></div><div class="line number17 index16 alt2"><code class="undefined spaces">    </code><code class="comments"># output string from (key,value) pairs</code></div><div class="line number18 index17 alt1"><code class="undefined spaces">    </code><code class="plain">output </code><code class="keyword">=</code> <code class="plain">''</code></div><div class="line number19 index18 alt2"><code class="undefined spaces">    </code><code class="keyword">for</code> <code class="plain">key,value </code><code class="keyword">in</code> <code class="functions">dict</code><code class="plain">.items():</code></div><div class="line number20 index19 alt1"><code class="undefined spaces">        </code><code class="plain">output </code><code class="keyword">=</code> <code class="plain">output </code><code class="keyword">+</code> <code class="plain">key </code><code class="keyword">+</code> <code class="functions">str</code><code class="plain">(value)</code></div><div class="line number21 index20 alt2"><code class="undefined spaces">    </code><code class="keyword">return</code> <code class="plain">output</code></div><div class="line number22 index21 alt1"> </div><div class="line number23 index22 alt2"><code class="comments"># Driver function</code></div><div class="line number24 index23 alt1"><code class="keyword">if</code> <code class="plain">__name__ </code><code class="keyword">=</code><code class="keyword">=</code> <code class="string">"__main__"</code><code class="plain">:</code></div><div class="line number25 index24 alt2"><code class="undefined spaces">    </code><code class="functions">input</code><code class="keyword">=</code><code class="string">"wwwwaaadexxxxxx"</code></div><div class="line number26 index25 alt1"><code class="undefined spaces">    </code><code class="functions">print</code> <code class="plain">(runLengthEncoding(</code><code class="functions">input</code><code class="plain">))</code></div></div></td></tr></tbody></table></div>

Output

w4a3d1e1x6

Another code:

Python3

def encode(message):
    encoded_message = ""
    i = 0
 
    while (i <= len(message)-1):
        count = 1
        ch = message[i]
        j = i
        while (j < len(message)-1):
            if (message[j] == message[j+1]):
                count = count+1
                j = j+1
            else:
                break
        encoded_message=encoded_message+str(count)+ch
        i = j+1
    return encoded_message
 
#Provide different values for message and test your program
encoded_message=encode("ABBBBCCCCCCCCAB")
print(encoded_message)

Output

1A4B8C1A1B

Feeling lost in the world of random DSA topics, wasting time without progress? It's time for a change! Join our DSA course, where we'll guide you on an exciting journey to master DSA efficiently and on schedule.
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 geeks!

Last Updated : 21 Jul, 2022

Count words in a given string

Anagram checking in Python using collections.Counter()

Share your thoughts in the comments

Run Length Encoding in Python

Python3

Python3

Please Login to comment...

What kind of Experience do you want to share?