Sequence Overview
Python has six built-in types of sequences. This chapter concentrates on two of the most common ones: lists and tuples.
The other built-in sequence types are strings (which I revisit in the next chapter ), Unicode strings, buffer objects, and xrange objects.
Common Sequence Operations
indexing,slicing,adding,multiplying, and checking for membership.
List Comprehension
List Comprehension is a way of making lists from other lists( similar to set comprehension, if you know that term form mathematics). It works in a way similar to for loops and is actually quite simple:
>>> [x*x for x in range(10)]
eval and exec
eval ( raw_input("enter an arithmetic expression:"))
input: 6 + 18 *2
42
exec('print "helloworld"')