
    In a dynamic ride-sharing system, write a function that identifies the first unique character in a ride request identifier to establish a quick reference point for request prioritization. The function should process a string containing alphanumeric ride request IDs and return the first character that appears exactly once in the identifier, which will be used for efficient request categorization in high-traffic scenarios.
    

    
def first_non_repeating_character(str1):
    """
    In a dynamic ride-sharing system, write a function that identifies the first unique character in a ride request identifier to establish a quick reference point for request prioritization. The function should process a string containing alphanumeric ride request IDs and return the first character that appears exactly once in the identifier, which will be used for efficient request categorization in high-traffic scenarios.
    

    """
def first_non_repeating_character(str1):
    """
    In a dynamic ride-sharing system, write a function that identifies the first unique character in a ride request identifier to establish a quick reference point for request prioritization. The function should process a string containing alphanumeric ride request IDs and return the first character that appears exactly once in the identifier, which will be used for efficient request categorization in high-traffic scenarios.
    

    """
    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