How to use lists in Python ?

Lists in Python

• most flexible ordered collection
• can contain any sort of object : numbers, strings and even other lists
• define a left to right positional ordering of the items
• can fetch a component object by indexing the list on the object’s offset : for slicing and concatenation
• Variable length : List can grow and shrink
• Heterogeneous : Lists may contain any sort of object

Defining list

>>> aa=[]   # An empty list

>>> aa=[1,2,3,4]   # 4 items, index 0-3

List responds to + and * operations like Strings

>>> aa=[1,2,3]

>>> bb=[4,5,6]

>>> aa+bb

>>> aa*3

Method len() to get size of list and "in" function

>>> aa=[1,2,3]

>>> len(aa)

>>> 3 in aa

append method adds item at end of the list

>>> aa=[]

>>> aa.append(1)

>>> aa.append(2)

>>> aa.append(3)

>>> aa.append(‘4’)

>>> aa.append(5.0)

sort method orders a list (in ascending)

>>> aa=[4,2,6,8,1,3,4,10]

>>> aa.sort()

reverse method reverses the list

>>> aa=[1,2,3,4]

>>> aa.reverse()

pop deletes an item from the end

>>> aa.pop()