A tuple is a sequence of values. The values can be any type, and they are indexed by integers, so in that respect tuples are a lot like lists. The important difference is that tuples are immutable. Syntactically, a tuple is a comma-separated list of values:
To create a tuple with a single element, you have to include the final comma. Without the comma, Python treats (‘a’) as a string in parentheses. Another way to create a tuple is the built-in function tuple. With no argument, it creates an empty tuple.
If the argument is a sequence (string, list or tuple), the result is a tuple with the elements of the sequence. Most list operators also work on tuples. And the slice operator selects a range of elements.
But if you try to modify one of the elements of the tuple, you get an error. You cant modify the elements of a tuple, but you can replace one tuple with another.
from Thinking in Python
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原文地址：http://www.cnblogs.com/ryansunyu/p/3846452.html
