# Run Length Encoding in Python

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

 `# 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`

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`

If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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!

Previous
Next