Python Basic - tuple introduction

tuple is an important build-in python data structure type. It is an ordered and immutable serial

How to declare a tuple

We can use the below statement to declare a tuple

       tuple_name = (elements1,element2,)     # this is call pack

       tuple_name = tuple (serial)

how to visit the elements in tuple:

tuple elements can be visited by index, the index is started with 0, if the index is beyound the length, the statement will generate an error

sample code:

>>> tuple_name=tuple("this is a test")

>>> print tuple_name

('t', 'h', 'i', 's', ' ', 'i', 's', ' ', 'a', ' ', 't', 'e', 's', 't')

>>> tuple_name[5]

'i'

>>> tuple_name[500]

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

IndexError: tuple index out of range

An interesting and powerful featuer is using minus index, minus index is the index counting from the end of the tuple. For example still with the above sample

>>> tuple_name[-1]

't'

>>> tuple_name[-3]

'e'

Unpack the tuple

When tuple is used as right element by assignment, it can be unpacked.

See below

>>> mytuple=[1,2,3,]

>>> a, b, c = mytuple

then a will be 1, b will be 2 and c will be 3. the length of the elements should be exactly the same as the length of the tuple

Slice: get the sub-tuple

We can get the sub-tuple by using slice, the format is tuple[first:last:step]

• First: the first element index for the slice (by default is the 0 if not specified)
• Last: the last element index for the slice(exclusive) (by default is the length of the tuple if not specified)
• Step: the step length (by default is 1)

Some sample

Mytuple[1:5] : from the 2^nd to 4^th element

Mytuple[10:] : from the 10^th to last elment

Mytuple[::2] : every other elment

tuple Traversal

Traversal is usually done by the index. We need to build-in functions len () and range ().

Sample code:

for index in range(len(mytuple)):

       dosomething(mytuple[index])