the first one returns only one value because each function returns only once, and then it's over. When the
second uses the map method, it substitutes each item of the x list into the normalize function for execution, putting a string in x into the normalize function at a time, so only the first letter is returned for the same reason as above (the loop in the function returns the result the first time). The following errors in
are all due to the fact that the capitalize method is a string, which list does not have.

-- supplement
the real logic when using map is like this:

    for i in 'sdas':
        return i.capitalize()
    for i in 'dsdwds':
        return i.capitalize()  

each execution only ends with the first letter.