trimrepeat.py

def delete_reoccurring_chars(string):
    """Return the string after deduplication.
    
    >>> delete_reoccurring_chars('metasotaaaa')
    'metasota'
    >>> delete_reoccurring_chars('mmeettaassoottaa')
    'metasota'
    >>> delete_reoccurring_chars('metasota')
    'metasota'
    >>> delete_reoccurring_chars('')
    ''
    """
    # your codes here
    if not string:
      return ''

    output = list(string)
    res = [output[0]]
    for i in range(1, len(output)):
        if res[len(res) - 1] != output[i]:
           res.append(output[i])
            
    return ''.join(res)
  
  
if __name__ == '__main__':
    import doctest 

    doctest.testmod()

更简明

扎眼的 res[len(res] - 1] = res[-1]

return ''.join(reduce(lambda x, y: x + y if x[-1] != y[0] else x,  [[i] for i in a]))

return reduce(lambda x, y: x + y if x[-1] != y else x, string[1:], string[0]) if string else ''

return reduce(lambda x, y: x + y if x and x[-1] != y else x, string) if string else ''