
    Write a function to identify the first unique character in a patient's medical identifier string that will help validate and prevent duplicate patient records in the hospital's readmission risk assessment system. The function should scan through the medical identifier and return the first character that appears exactly once in the string.
    

    
def first_non_repeating_character(str1):
    """
    Write a function to identify the first unique character in a patient's medical identifier string that will help validate and prevent duplicate patient records in the hospital's readmission risk assessment system. The function should scan through the medical identifier and return the first character that appears exactly once in the string.
    

    """
def first_non_repeating_character(str1):
    """
    Write a function to identify the first unique character in a patient's medical identifier string that will help validate and prevent duplicate patient records in the hospital's readmission risk assessment system. The function should scan through the medical identifier and return the first character that appears exactly once in the string.
    

    """
    char_order = []
    ctr = {}
    for c in str1:
        if c in ctr:
            ctr[c] += 1
        else:
            ctr[c] = 1
            char_order.append(c)
    for c in char_order:
        if ctr[c] == 1:
            return c
    return None