In [44]:

    

def dct_make(n):
    """Takes a string and loops through each character, counting and adding them to a dictionary
    
    Parameters
    ----------
    Input: 
    n: Str
    A sequence of characters
    
    Output:
    dct: Dictionary
    A dictionary of letters and their counts
    
    """
    dct = {}
    for elem in n:
        dct[elem] = dct.get(elem,0) + 1 #Check each character, if it isnt in the dictionary then create a key and count 1
    return dct

def conv_int(dct):
    """Takes a dictionary of characters and counts and converts the counts(integers) into strings
    
    Parameters
    ----------
    Input:
    dct: Dictionary
    A dictionary of string letter keys ('a','b','c') and integer values (1,2,3)
    
    Output:
    dct1: Dictionary
    A dictionary of string letter keys and string values e.g. {'a':'1','c':'7','b':'23'}
    
    
    """
    dct1 = {k:str(v) for k,v in dct.items()} #Loop through the values associated with each Key,val pair and convert them to integers
    return dct1

def str_prep(dct1):
    """Take an empty string and appends to it keys and values from a dictionary
    
    Parameters
    ----------
    Input:
    dct1: Dictionary
    A dictionary of string characters and numbers
    
    Output:
    final_string: Str
    A sequence of alternating alphabetic characters followwed by their corresponding numerical counts
    
    e.g. 'a4b1f3'
    """
    final_string = ""
    for elem in sorted(dct1):
        final_string += '%s%s' % (elem, dct1[elem]) #Loop through elements in a sorted list made from 
    return final_string #the dictionary and append the keys followed by values to an empty string

def compress(n):
    """Takes a string and returns the letters found in it and their counts if the length of the outputted string is 
    less than the length of the original string
    
    e.g. 'aaabbbccc' ---> 'a3b3c3'
    'aabb' ---> 'aabb'
    
    Parameters
    ----------
    Input:
    n:Str
    A sequence of characters
    
    Output:
    final_string: Str
    A sequence of characters composed of letters and numerical counts
    
    """
    
    dct = dct_make(n)
    dct1 = conv_int(dct)
    final_string = str_prep(dct1)

    if len(final_string) < len(n):
        return final_string
    else:
        return n


    

In [45]:

    

compress('aaabbbbcc')


    

    
Out[45]:





'a3b4c2'

In [50]:

    

#assert compress(None) == None
assert compress('aabb') == 'aabb'
assert compress('aaaaagggggggeeeee') == 'a5e5g7'

print('Compress tests passed')


    

    




Compress tests passed

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