# Run Length Encoding in Python

• Difficulty Level : Hard
• Last Updated : 21 Jul, 2022

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'```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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`

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