Exercises:

Objects:

1. Check the example "star.py", for each exercise you shoud test the new code in the main function.
	a) Define a new class variable AU, that represents the unit of distance from the Sun to the Earth (149 597 871 Km).
	b) Implement the __str__ method to the class so we can easily read the content
	c) Overload the + operator (__add__). So the result of the two stars is simply the sum of the massses and the root square of the sum of the radius.
	
Homework/Extra:	
2. 	Create new class planet: "planet.py". (ideas for object variables: planetary_radius, planetary_mass, eccentricity, Period, distance to star, life?).

3. Create a new plass Planetary_System. 
	a) This class must have a star (from star.py) and a list of planets to represent the planets
	b) Create a method to compute the total mass of the planets in the planetary system.



Numpy

1. Import the numpy package under the name np

2. Create a null vector of size 10

3. Create a null vector of size 10 but the fifth value which is 1
	
4. Create a vector with values ranging from 10 to 99
	
5. Create a 3x3 matrix with values ranging from 0 to 8

6. Find indices of non-zero elements from [1,2,0,0,4,0]

7. Declare a 3x3 identity matrix
	
8.  a) Declare a 10x10x10 array with random values
    b) Generate an array with 10 random numbers extracted from a poisson distribution with \lambda = 5:
	
9. Declare a 8x8 matrix and fill it with a checkerboard pattern

10. a) Declare a 10x10 array with random values and find the minimum and maximum values
    b) Generate an array with random 100 integer numbers, ranging from 5 to 97. Check the mean of the even numbers.
    c) Generate an  array with 5 numbers for 1 to 50. Make sure there is no numbers repeated in the selected 5.

11. Normalize a 5x5 random matrix (between 0 and 1)
	
12. a) Multiply a 3x3 matrix by a 3x3 matrix 
    b) Multiply a 5x3 matrix by a 3x2 matrix (real matrix product)
    c) Multiply a 5x3 matrix by a 3x2 matrix (real matrix product)
    d) try to multiply a 5x3 matrix by a 3x2 matrix

13. Create a vector of size 1000 with values ranging from 0 to 1, both excluded
	
14. Create a random vector of size 100 and sort it, and find its mean value
	
15. Create random vector of size 100 and replace the maximum value by 0

16. Generate a generic 2D Gaussian-like array

17. Find the nearest value from a given value in an array

18. Consider the following file:

1,2,3,4,5
6,,,7,8
,,9,10,11

How to read it ?