about python

1. Lists
List can store a sequence of values belonging to any datatype.
'Hi' 3 2.6 ‘S’ ‘Two’
L = [‘Hi’, 3, 2.6, ‘S’, ‘Two’] or L = list(<sequence>)
L :

2. Playing with Lists
■ Creating Lists
L = list(‘LockDown’)
print(L) [‘L’, ‘o’, ‘c’, ‘k’, ‘D’, ‘o’, ‘w’, ‘n’]
L = list( input(‘Enter elements : '))
print(L)
Takes one string, make each character as one element in List.

3. Playing with Lists
■ Lists vs Strings
Similarities :
Len( ), Indexing & Slicing, Membership, Concatenation & Replication
Differences :
Storage : Strings store single character at each block, Lists store references.
Mutability : Strings-Immutable Lists-Mutable

4. Playing with Lists
■ Appending Elements
L=[2,5,17]
L[3]=12 or L.append(12)
■ Updating Elements
L[1]=7
■ Deleting Elements
del L[2] deletes element at index 2.
del L[1:4] deletes slice of 1:4 i.e. 1,2 & 3 indices.
del L deletes the whole list.
■ Extending Elements
L = [2,5,17]
L.extend( (21, ‘hi’, [3,6,7]) )

5. Playing with Lists (other operations are same as strings)
■ Making a True Copy
Colors = [‘red’, ‘blue’, ‘green’]
L2 = Colors ❌
L2 = list(Colors) ✔
In first case, any changes in Colors will reflect in L2 as they both are
referencing the same list.

6. Lists Functions
Python also offers many built in functions for Lists.
● The index method gives the index of the <element>
L.index(<element>) exception error if not found.
● The extend method
L.extend(<list>) appends <sequence> into L.
append( ) & extend( ) discussed before

7. Lists Functions
● The insert method
L.insert(<pos>,<item>) inserts <item> at <pos>th
index.
● The pop method
L.pop(<index>) deletes & returns element at <index>.
L.pop( ) deletes & returns last element.

8. Lists Functions
● The remove method
L.remove(<value>) removes the first occurence of <value>.
● The clear method
L.clear( ) clears the whole list,
[ ], this remains.
● The count method
L.count( <item>) counts the <item> & returns

9. Lists Functions
● The reverse method
L.reverse( ) reverses the whole list.
● The sort method
L.sort( ) sorts the list in ascending order.
L.sort(reverse = True) sorts the list in descending order.

10. Practice Time
Q1. List=[1,2,3,4,5,6,7,8,9]
print(List[ : : 3])
Q2. What will be the output of the following code snippet?
a. A = [ ]
for i in range(1,4) :
A.append(i)
print(values)
b. b=[ 1,2,3,4,5 ]
print( b[3:0:-1] )

11. Tuples
Tuples are basically immutable Lists.
Lists are made by square brackets [ ].
Tuples are made by curved brackets ( ).
t=(1, 'hello', 3.2, ‘w’)
t=tuple('Harsh')

12. Tuples vs Lists
Following things are same as before :-
● Creating
● Creating using input
● Indexing & Slicing
● Membership
● Concatenation & Replication
● Traversing

13. T = (1, 2, ‘A’, ‘B’)
w, x, y, z = T variables on the left side must match
the number of elements in tuple.
print(w,x,y,z,sep=’*’)
OUTPUT : 1*2*A*B
Unpacking a Tuple

14. Tuple Functions
● The len method (same for string & List too)
len(<tuple>) returns length of the tuple.
● The max/min methods
max(<tuple>) returns max element in the<tuple>.
min(<tuple>) returns min element in the<tuple>.

15. ● The index method returns index number of <item>.
t.index(<item>) exception error if not found.
● The count method
t.count(<item>) returns the count of <item> in the tuple.
● The tuple method used to create tuples.
t=tuple('abc') (‘a’, ‘b’, ‘c’)
t=tuple([1,2,3]) tuple from list
t=tuple( ) empty tuple
Tuple Functions

16. Practice Time
Q1. t = ‘a’ , ‘b’
t2= (‘a’, ‘b’)
print(t==t2)
Q2. What is the length of this tuple?
t=( ( ( (‘a’,1 ), ‘b’, ‘c’ ), ‘d’, 2 ), ‘e’, 3 )
Q3. A= ( ‘Hello’, ‘Harsh’ , ‘How’re’, ‘you ?’ )
( a,b,c,d ) = A
print( a, b, c, d )
A = ( a, b, c, d )
print( A[0][0]+A[1][1], A[1] )