How come string.maketrans does not work in Python 3.1?

I'm a Python newbie.

How come this doesn't work in Python 3.1?

from string import maketrans   # Required to call maketrans function.

intab = "aeiou"
outtab = "12345"
trantab = maketrans(intab, outtab)

str = "this is string example....wow!!!";
print str.translate(trantab);

When I executed the above code, I get the following instead:

Traceback (most recent call last):
  File "<pyshell#119>", line 1, in <module>
    transtab = maketrans(intab, outtab)
  File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/string.py", line 60, in maketrans
    raise TypeError("maketrans arguments must be bytes objects")
TypeError: maketrans arguments must be bytes objects

What does "must be bytes objects" mean? Could anyone please help post a working code for Python 3.1 if it's possible?

Solution

Strings are not bytes.

This is a simple definition in Python 3.

Strings are Unicode (which are not bytes) Unicode strings use "..." or '...'

Bytes are bytes (which are not strings) Byte strings use b"..." or b'...'.

Use b"aeiou" to create a byte sequence composed of the ASCII codes for certain letters.