I just typed the following at my shell prompt, and it worked just fine:
$ python
Python 2.7.3 (default, Aug 1 2012, 05:16:07)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> my_age = 35
>>> my_eyes = 'Blue'
>>> print "my age is %d and my eye color is %s" % (my_age, my_eyes)
my age is 35 and my eye color is Blue
>>>
The way to type more than one line of code in the interactive Python interpreter is, well, to type more than one line of code in the interactive Python interpreter. I'd think that would be good enough for your purposes.
It's true that you'll get a new prompt after each line, which means that if two of your lines of code produce output, that output will be separated by prompts. I guess that's what you're concerned about, though the example in your question doesn't suggested that:
$ python
Python 2.7.3 (default, Aug 1 2012, 05:16:07)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print "first line"
first line
>>> print "second line"
second line
>>>
If that's a problem, you can enclose your multiple statements in a (properly indented!) if
statement:
$ python
Python 2.7.3 (default, Aug 1 2012, 05:16:07)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> if 1:
... print "first line"
... print "second line"
...
first line
second line
>>>
(I'd suggest, even though it doesn't answer your question, that if you're writing code that's complex enough for this to matter, you should be writing scripts. Perhaps you've started doing so in the year and a half since you posted the question.)