Python training : Lists and Tuples

 

Lists

>>> a = [10,20,30,40,50,60,70,80,90]
>>> len(a)
9
>>> min(a)
10
>>> max(a)
90
>>> print (a + [100,110,120])
[10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]

>>> print (a[0])
10
>>> a[0]=15
>>>print ( a)
[15, 20, 30, 40, 50, 60, 70, 80, 90]

>>> del a[2]
>>> print (a)
[15, 20, 40, 50, 60, 70, 80, 90]

>>> print (a[1:5])
[20, 30, 40, 50]


>>> a[1:5]=[200,300,400,500]
>>> print (a)
[10, 200, 300, 400, 500, 60, 70, 80, 90]

>>> a[1:5] = []
>>>print( a)
[10, 60, 70, 80, 90]

>>> a[:] = []
>>>print(a)
[]
>>> a = [1,2,3]
>>> print (a*3)
[1, 2, 3, 1, 2, 3, 1, 2, 3]


Python Slicing examples

a=[0,11,22,33,44,55,66,77,88,99]


syntax of slicing: a[x:y:z]

>>> a[0:7:1]    #elements from 0 (included) to 7 (excluded)
[0, 11, 22, 33, 44, 55, 66]

>>> a[0:7:2]
[0, 22, 44, 66]

If z is not given, z is taken as 1
>>> a[0:7]
[0, 11, 22, 33, 44, 55, 66]


If z is positive , slicing will be from left to right , so x should be less than y.


>>> a[2:7:1] 
[22, 33, 44, 55, 66]

>>> a[7:2:1]  (will not slice)
[]
>>> 

If z is negative ,slicing will be from right to left, so x should be greater than y

>>> a[7:2:-1]
[77, 66, 55, 44, 33]


if z is positive and 
	if x is not given ,  x is taken as 0 
	if y is not given ,  y is taken as the length of the list

>>> a[:7:1]
[0, 11, 22, 33, 44, 55, 66]

>>> a[5::1]
[55, 66, 77, 88, 99]

if z is negative and
	if x is not given , x is taken as -1 (index of the last element)
	if y is not given , y is taken as negative of length of the list

>>> a[:-5:-1]
[99, 88, 77, 66]

>>> a[-5::-1]
[55, 44, 33, 22, 11, 0]


>>> a[5:-1:1]	
[55, 66, 77, 88]

>>> a[-1:5:-1]
[99, 88, 77, 66]

List inside list

>>> a = [10,20,[30,40,50],60]
>>> print (a)
[10, 20, [30, 40, 50], 60]

>>> print (a[2])
[30, 40, 50]
>>> print (a[2][0])
30
>>> print (a[2][1])
40

List methods

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

>>> a=[1,2,3]
>>> a.append(4)
>>> print(a)
[1, 2, 3, 4]

>>> a.append([5,6])
>>> print(a)
[1, 2, 3, 4, [5, 6]]

>>> a.extend([7,8,9])
>>> print (a)
[1, 2, 3, 4, [5, 6], 7, 8, 9]

>>> a=[10,20,30,40,50,60,70]
>>> a.pop()
70
>>>print( a)
[10, 20, 30, 40, 50, 60]
>>> a.pop(2)
30
>>> print(a)
[10, 20, 40, 50, 60]
An element can be removed using “remove” method also. 
	pop() takes index as the argument and remove() takes the element as argument.

>>> a=[10,20,30,40,50]
>>> a.remove(30)
>>> a
[10, 20, 40, 50]

 >>> a=[10,20,30,40,50]
>>>a.insert(2,25)
>>> print(a)
[10, 20, 25, 30, 40, 50]

>>> a = [10,20,30,40,50]
>>> a.reverse()
>>> print(a)
[50, 40, 30, 20, 10]

>>> a=[8,2,15,4,6,20]
>>> a.sort()
>>> print(a)
[2, 4, 6, 8, 15, 20]
>>> a.sort(reverse=True)
>>> print(a)
[20, 15, 8, 6, 4, 2]

Tuple

Tuple is like a list , but it is immutable. (Tuple does not allow to add,del,insert,modify  elements)
Tuple use parentheses, whereas list use square brackets.

Tuple methods

>>> a=(10,20,30,40,50)
>>> len(a)
5

>>> min(a)
10

>>> max(a)
50

>>> a.count(50)
1

>>> a.index(50)
4

>>> a=(10,20,30,40,50)
>>> b = (60,70)
>>> c = a + b
>>> print (c)
(10, 20, 30, 40, 50, 60, 70)
>>> a * 2
(10, 20, 30, 40, 50, 10, 20, 30, 40, 50)

Python Exercises

1. Write a python program to find the sum of all numbers in a list

2. Write a python program to find largest number in a given list with out using max() 

3. Write a python program to find the common numbers from two lists 

4. Write a python program to print all even numbers from a given list

5. Write a python program to create a list of even numbers and another list of odd numbers from a given list

6. Write a python program to remove repeated elements from a given list without using built-in methods

7. Write a python program to find the longest word in a given sentence

8. Write a python program to find number of occurrences of given number with out using built-in methods

9. ["www.zframez.com", "www.wikipedia.org", "www.asp.net", "www.abcd.in"]
Write a python program  to print website suffixes (com , org , net ,in)  from this list

10. Write a python program to sort a given list of numbers with out using sort() function



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