collection

List

• Lists Are Ordered i.e. Its elements can be accessed by using Index.
• Lists Can Contain Arbitrary Objects. i.e. any type of objects.
• Lists Are Mutable. i.e. contents of list can be changed.
• Lists Are Dynamic. i.e. contents can be added or removed.
• List can contain duplicate values.
• Lists Can Be Nested. i.e. a list can contain another collection in it.

<list_name>=[value1,value2,value3,...,valueN]

lst=[4,3,1,6,2]
print(lst)
for n in lst:
 print(n)

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

lst=[4,3,1,6,2]
s=0
for n in lst:
 s=s+n
print("Sum is ",s)

Accessing elements

• Individual elements in a list can be accessed using an index in square brackets.
• List indexing in Python is zero-based: the first item in the list has index 0, the next has index 1, and so on.
• The index of the last item will be the length of the list minus one.

<list_name>[index]

<list_name>[startindex:stopindex:step]

• indicates beginning of sublist
• Default is zero
• Sublist includes element from start index

• indicates end of sublist
• Default is end of list
• Sublist excludes element from stop index

• Indicates next element
• Default is 1

lst = [ 4, 3, 1, 6, 2, 9, 0 ]
print( lst[ 2 ] )
print( lst[ 0 ] )
print( lst[ -1 ] )
print( lst[ 2 : 5 ] )
print( lst[ : 5] )
print( lst[ 2: ] )
print( lst[ : :2 ] )
print(lst[1:5:2])

1
4
0
[1,6,2]
[4,3,1,6,2]
[1,6,2,9,0]
[4,1,2,0]
[3,6]

lst = [ 4, 3, 1, 6, 2, 9, 0 ]
print( lst[ -5: -2 ] )
print( lst[ -6:-2:2 ] )
print(lst[-2:-6:-2])
print( lst[ : :-1 ] )

[1,6,2]
[3,6]
[9,6]
[0,9,2,6,1,3,4]

lst = [ 'ram','shyam','gopal','amit','raj' ]
i=0
for nm in lst:
print(i,"-",nm)
i=i+1

0 – ram
1 – shyam
2 – gopal
3 – amit
4 – raj

enumerate(iterable, start=0)