Python List and Tuple

List and Tuple are the two very useful build-in sequences in Python.

• List: an ordered sequence which can be changed. Insert, delete, update. [element1, element2]
• Tuple: an ordered sequence which are immutable. It is faster than List. (element1, element2)

Common Methods:

1.       index: the sequence have indexes, starting from 0.  minus index indicates started from the right.

>>> #define a list

>>> mylist=['one','two','three']

>>> mylist[0]

'one'

>>> mylist[2]

'three'

>>> mylist[-1]

'three'

>>> 

2.       slice : get the range from the existing sequence, minus index (means from the right) or no index (means from start or end)

>>> mynumbertuple=(1,2,3,4,5,6,7,8,9,10,)

>>> mynumbertuple[3:5]

(4, 5)

>>> mynumbertuple[3:-3]

(4, 5, 6, 7)

>>> print mynumbertuple[-3:]

(8, 9, 10)

>>> print mynumbertuple[3:]

(4, 5, 6, 7, 8, 9, 10)

3.       plus (+) : join the same type of sequence together.

>>> mylist = [1,2,3,] + [4,’5’,6]

>>> print mylist

[1, 2, 3, 4, ‘5’, 6]

4.       multiply (*) : repeat the sequence with multiple times.

>>> mynewtuple = (1,2,3)*3

>>> print mynewtuple

(1, 2, 3, 1, 2, 3, 1, 2, 3)

5.       in - check if the memer is in the sequence.

>>> mynumbertuple

(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

>>> 2 in mynumbertuple

True

>>> 10 in mynumbertuple

True

>>> 20 in mynumbertuple

False

6.       len, min, max build-in functions.

• len: get the length of the sequence
• min, get the min value of the sequence
• max, get the max value of the sequence

>>> len(mynumbertuple)

10

>>> max(mynumbertuple)

10

>>> min(mynumbertuple)

1

Because the list is mutable, there are a few useful functions for list.

1.       set the value

list[index] =  newvalue

2.       delete value

del list[index]

or tricky way list[index] = []

>>> mylist = [1,2,3,4,5]

>>> mylist[3]=40                 #set the 3^rd element to 40

>>> mylist

[1, 2, 3, 40, 5]

>>> del mylist[-1]                #delete the last element

>>> mylist

[1, 2, 3, 40]

>>> mylist[1:2] = []             #delete the 2^nd element.

>>> mylist

[1, 3, 40]

3.       append(): add one object to the list

4.       extend(): combine the new list to the previous list

>>> list1=[1,2,3]

>>> list2=[1,2,3]

>>> list1.append([4,5,6])

>>> list1

[1, 2, 3, [4, 5, 6]]

>>> list2.extend([4,5,6])

>>> list2

[1, 2, 3, 4, 5, 6]

5.       count(). Count the counters in the sequence for an element.

>>> [1,2,3,4,1,2,3,5].count(3)

2

6.       index(). Get the first index of the element

>>> [1,2,3,5,1,2,3,5].index(5)

7.       remove(): remove the first matched element from the list

>>> mylist = [1,3,5,7,2,4,6,8,5]>>> mylist.remove(5)>>> mylist[1, 3, 7, 2, 4, 6, 8, 5]

8.       sort(): sort the elements

>>> mylist.sort()

>>> mylist

[1, 2, 3, 4, 5, 6, 7, 8]

9.       reverse(): reverse the elements

>>> mylist.reverse()

>>> mylist

[8, 7, 6, 5, 4, 3, 2, 1]