import string


def full_clean_cxr(sentence):
    """Removes whitespace from beginning and end of a sentence. Lowercases.
    Replaces punctuation (except periods) with a space. Removes multiple spaces."""
    sentence = sentence.strip()
    sentence = sentence.lower()
    
    #replace punctuation with a space
    for punc in string.punctuation.replace('.',''): #for all punctuation except a period
        sentence = sentence.replace(punc,' ')
    
    #replace multiple whitespace with single
    sentence = ' '.join(sentence.split()) 
    
    #remove period from the end of sentence (don't remove all periods to
    #preserve decimal measurements of lesions)
    sentence = sentence.strip('. ')
    return sentence