np.random.rand() and random arrays in NumPy - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a 1D array of 5 random numbers between 0 and 1 using numpy.

NumPy

import numpy as np
random_array = np.random.[1](5)
print(random_array)

Drag options to blanks, or click blank then click option'

Arandom

Brandint

Crand

Drandn

Attempts:

3 left

💡 Hint

Common Mistakes

Using np.random.randint which generates integers, not floats.

Using np.random.randn which generates numbers from a normal distribution.

The np.random.rand() function generates random numbers between 0 and 1. Here, rand(5) creates an array of 5 such numbers.

2fill in blank

medium

Complete the code to create a 2D array with 3 rows and 4 columns of random numbers between 0 and 1.

NumPy

import numpy as np
array_2d = np.random.[1](3, 4)
print(array_2d)

Drag options to blanks, or click blank then click option'

Arand

Brandint

Crandom_sample

Drandn

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a tuple instead of separate arguments to rand.

Using randint which generates integers.

np.random.rand(3, 4) creates a 2D array with 3 rows and 4 columns filled with random floats between 0 and 1.

3fill in blank

hard

Fix the error in the code to generate a 1D array of 10 random floats between 0 and 1.

NumPy

import numpy as np
random_numbers = np.random.rand([1])
print(random_numbers)

Drag options to blanks, or click blank then click option'

A[10]

B10

C(10,)

Drange(10)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a list or tuple instead of an integer.

Using range(10) which is not accepted.

The np.random.rand() function expects dimensions as separate integer arguments, not a list or tuple. So, rand(10) creates a 1D array of length 10.

4fill in blank

hard

Fill both blanks to create a dictionary where keys are numbers 1 to 5 and values are their random floats between 0 and 1.

NumPy

import numpy as np
random_dict = {i: np.random.[1]() for i in range(1, [2])}
print(random_dict)

Drag options to blanks, or click blank then click option'

Arand

Brandint

C6

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using randint which generates integers.

Using 5 as the stop value, which excludes 5 in range.

np.random.rand() generates a random float between 0 and 1. The range goes up to 6 to include numbers 1 through 5.

5fill in blank

hard

Fill all three blanks to create a 3x3 numpy array of random floats and print its shape and type.

NumPy

import numpy as np
arr = np.random.[1]([2], [3])
print(arr.shape)
print(type(arr))

Drag options to blanks, or click blank then click option'

Arand

B3

Drandint

Attempts:

3 left

💡 Hint

Common Mistakes

Using randint which generates integers.

Passing dimensions as a tuple instead of separate arguments.

np.random.rand(3, 3) creates a 3 by 3 array of random floats between 0 and 1. The shape prints as (3, 3) and the type is numpy.ndarray.

Practice

1. What does the function np.random.rand(3, 2) do in NumPy?

easy

A. Creates a 3x2 array with random floats between 0 and 1

B. Creates a 3x2 array filled with zeros

C. Creates a 3x2 array with random integers

D. Creates a 3x2 array filled with ones

Solution

1. Step 1: Understand np.random.rand() function

   This function generates random floats between 0 and 1.

2. Step 2: Analyze the shape arguments (3, 2)

   The arguments specify the shape of the output array as 3 rows and 2 columns.

3. Final Answer:

   Creates a 3x2 array with random floats between 0 and 1 -> Option A

4. Quick Check:

   np.random.rand(3, 2) = 3x2 random floats [OK]

Hint: Remember rand() outputs floats in [0,1) with given shape [OK]

Common Mistakes:

• Thinking it creates integers instead of floats
• Confusing shape arguments with array values
• Assuming it creates zeros or ones

2. Which of the following is the correct syntax to create a 1D array of 5 random floats using np.random.rand()?

easy

A. np.random.rand(5)

B. np.random.rand[5]

C. np.random.rand((5))

D. np.random.rand{5}

Solution

1. Step 1: Recall correct function call syntax

   Functions use parentheses () to pass arguments, not brackets [] or braces {}.

2. Step 2: Check argument for array size

   Passing 5 inside parentheses creates a 1D array of length 5.

3. Final Answer:

   np.random.rand(5) -> Option A

4. Quick Check:

   Correct function call uses parentheses ( ) [OK]

Hint: Use parentheses () for function calls, not brackets or braces [OK]

Common Mistakes:

• Using square brackets [] instead of parentheses
• Using curly braces {} which are invalid syntax
• Adding extra parentheses unnecessarily

3. What is the shape and type of the output from this code?

import numpy as np
arr = np.random.rand(2, 4)
print(arr.shape, type(arr))

medium

A. (4, 2) <class 'numpy.ndarray'>

B. (2, 4) <class 'list'>

C. (2, 4) <class 'numpy.ndarray'>

D. (4, 2) <class 'list'>

Solution

1. Step 1: Understand np.random.rand(2, 4) output

   This creates a NumPy array with shape (2, 4) filled with random floats.

2. Step 2: Check the type of the variable arr

   It is a NumPy ndarray, not a Python list.

3. Final Answer:

   (2, 4) <class 'numpy.ndarray'> -> Option C

4. Quick Check:

   Shape and type match NumPy array output [OK]

Hint: np.random.rand dims = shape; output is always ndarray [OK]

Common Mistakes:

• Confusing shape order (2,4) vs (4,2)
• Thinking output is a Python list
• Misreading print output format

4. Identify the error in this code snippet:

import numpy as np
arr = np.random.rand[3, 3]
print(arr)

medium

A. Shape arguments should be strings

B. Missing import statement for numpy

C. Incorrect print syntax

D. Using square brackets [] instead of parentheses () for function call

Solution

1. Step 1: Check function call syntax

   np.random.rand is a function and must be called with parentheses (), not square brackets [].

2. Step 2: Verify other parts of code

   Import is correct, print syntax is valid, shape arguments are integers as required.

3. Final Answer:

   Using square brackets [] instead of parentheses () for function call -> Option D

4. Quick Check:

   Function calls need parentheses ( ) [OK]

Hint: Always use () to call functions, not [] [OK]

Common Mistakes:

• Using [] instead of () for function calls
• Assuming shape args must be strings
• Thinking print syntax is wrong

5. You want to create a 2D array with 3 rows and 4 columns filled with random floats between 0 and 1, then multiply all values by 10 to scale them. Which code correctly does this?

hard

A. arr = np.random.rand(12) * 10

B. arr = np.random.rand(3, 4) * 10

C. arr = np.random.rand(3) * 4 * 10

D. arr = np.random.rand(3, 4) + 10

Solution

1. Step 1: Create a 3x4 array of random floats

   Use np.random.rand(3, 4) to get a 2D array with 3 rows and 4 columns.

2. Step 2: Scale all values by 10

   Multiply the entire array by 10 to scale values from [0,1) to [0,10).

3. Final Answer:

   arr = np.random.rand(3, 4) * 10 -> Option B

4. Quick Check:

   Shape and scaling done correctly [OK]

Hint: Multiply after rand() to scale values, keep shape in arguments [OK]

Common Mistakes:

• Adding 10 instead of multiplying
• Using wrong shape arguments
• Creating 1D array instead of 2D