UTF_16 question

Hi everyone,
one thing that I do not understand is happening to me: I have some text
files with different characteristics, among these there are that they
have an UTF_32_le coding, utf_32be, utf_16_le, utf_16_be all of them
without BOM. With those utf_32_xx I have no problem but with the
UTF_16_xx I have. If I have an utf_16_le coded file and I read it with
encoding='utf_16_le' I have no problem I read it, with
encoding='utf_16_be' I can read it without any error even if the data I
receive have the inverted bytes. The same thing happens with the
utf_16_be codified file, I read it, both with encoding='utf_16_be' and
with 'utf_16_le' without errors but in the last case the bytes are
inverted. What did I not understand? What am I doing wrong?
thanks in advance