Python-NumPy

1.       Write the command for the following:

(a)  Print the NumPy version.

(b)  Create a Null array X of size 10.

(c)   Create a 1D Y array with values ranging from 10 to 49

2.       Create an array starting from 0 with an interval of 2 till 20.

3.       Convert a 1D array to a 2D array with 2 rows

4.       Create 3 X 3 identity matrix

5.       Create a 3 X 3 matrix with values ranging from 0 to 8

6.       Create a 3 X 3 NumPy array of all True’s

7.       Create a 1D array of length 10 & all elements initialized with value 7.

8.       Create a 2D array of 4 rows and 5 columns and all elements initialized with value 9.

9.       Write a NumPy program to test whether none of the elements of a given array is zero

10.   Write a NumPy program to create an array of 10 zeros, 10 ones, 10 fives.

11.   Write Write a NumPy program to create a 10X 10 matrix, in which the elements on the borders will be equal to 1 and inside 0.

12.   Write a NumPy program to compute sum of all elements, sum of each column and sum of each row of a given array

13.   Write a Numpy program to convert a given array into a list and then convert it into a list again

14.    Write a NumPy program to create a null vector of size 10 and update sixth value to 11.

15.   Write a NumPy program to create a 3X3 matrix with values ranging from 2 to 10

16.   Write a NumPy program to access an array by column

17.   How can we create a Boolean array?

18.   Write a NumPy program to extract all odd numbers from an array.

19.   Write a NumPy program to replace all odd numbers in an array with -1 without changing it.

20.   Write a NumPy program to convert a 1D array with 2 rows.

  

# Write a program to print all odd numbers from NumPy array. For example, if an array a contains the following values:

[10, 21, 4, 45, 66, 93] then result will be:

The odd numbers are: 21 45 93

#Program to print odd numbers from a NumPy array

import numpy as np

a=np.array([10,21,4,45,66,93])

for num in a:

    if num%2!=0:

        print(num,"\t",end="")

#Write a program to copy the content of an array A to another array B, replacing all odd numbers of array A with -1 without altering the original array A. Also, print both the arrays. For example, if the input array A is:

The array A is [10 51 2 18 4 31 13 5 23 64 29]

The result will be:

The array B is [10 -1 2 18 4 -1 -1 -1 -1 64 -1]

import numpy as np

A=np.array([10,21,4,45,66,93])

B=np.zeros(A.size, dtype=int)                      # Create array B of integer type with same size of A

ctr=0                                                               # to set the index position in array B

for num in A:

    if num%2!=0:                                                 # if the number is odd

        B[ctr]=-1

    else:

        B[ctr]=num

    ctr=ctr+1

print("Tha Array A is", A)

print("Tha Array B is", B)

Output:

The Array A is [10 21  4 45 66 93]

The Array B is [10 -1  4 -1 66 -1]

# Python code to find mean of every numpy array in list

  

# Importing module

import numpy as np

  

# List Initialization

Input = [np.array([1, 2, 3]),

         np.array([4, 5, 6]),

         np.array([7, 8, 9])]

  

# Output list initialization

Output = []

  

# using np.mean()

for i in range(len(Input)):

   Output.append(np.mean(Input[i]))

  

# Printing output

print(Output)

#Write a Python program to create an array of 5 integers and display the array items. Access individual element through indexes.

array_num = [1,3,5,7,9]

for i in array_num:

    print(i)

print("Access first three items individually")

print(array_num[0])

print(array_num[1])

print(array_num[2])

1

3

5

7

9

Access first three items individually

1

3

5

# Write a Python program to append a new item to the end of the array.

array_num = [1, 3, 5, 7, 9]

print("Original array: "+str(array_num))

print("Append 11 at the end of the array:")

array_num.append(11)

print("New array: "+str(array_num))

Original array: [1, 3, 5, 7, 9]Append 11 at the end of the array:New array: [1, 3, 5, 7, 9, 11]
Original array: [1, 3, 5, 3, 7, 1, 9, 3]
Reverse the order of the items:
[3, 9, 1, 7, 3, 5, 3, 1]
Original array: [1, 3, 5, 3, 7, 9, 3]
Number of occurrences of the number 3 in the said array: 3
Original array: [1, 3, 5, 7, 9]
Insert new value 4 before 3:
New array: [1, 4, 3, 5, 7, 9]
Original array: [1, 3, 5, 7, 9]
Remove the third item form the array:
New array: [1, 3, 7, 9]
Original array: [1, 3, 5, 3, 7, 1, 9, 3]
Remove the first occurrence of 3 from the said array:
New array: [1, 5, 3, 7, 1, 9, 3]
x

# Write a Python program to reverse the order of the items in the array.

array_num = [1, 3, 5, 3, 7, 1, 9, 3]

print("Original array: "+str(array_num))

array_num.reverse()

print("Reverse the order of the items:")

print(str(array_num))

# Write a Python program to get the number of occurrences of a specified element in an array.

array_num = [1, 3, 5, 3, 7, 9, 3]

print("Original array: "+str(array_num))

print("Number of occurrences of the number 3 in the said array: 
"+str(array_num.count(3)))

# Write a Python program to insert a new item before the second element in an existing array.

array_num = [1, 3, 5, 7, 9]

print("Original array: "+str(array_num))

print("Insert new value 4 before 3:")

array_num.insert(1, 4)

print("New array: "+str(array_num))

# Write a Python program to remove a specified item using the index from an array.

array_num =[1, 3, 5, 7, 9]

print("Original array: "+str(array_num))

print("Remove the third item form the array:")

array_num.pop(2)

print("New array: "+str(array_num))

# Write a Python program to remove the first occurrence of a specified element from an array

array_num = [1, 3, 5, 3, 7, 1, 9, 3]

print("Original array: "+str(array_num))

print("Remove the first occurrence of 3 from the said array:")

array_num.remove(3)

print("New array: "+str(array_num))