np.ones() for one-filled arrays in NumPy - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a 1D array of length 5 filled with ones.

NumPy

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

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

Aones

Bzeros

Cempty

Dfull

Attempts:

3 left

💡 Hint

Common Mistakes

Using np.zeros() which creates an array of zeros instead of ones.

Using np.empty() which creates an uninitialized array.

The np.ones() function creates an array filled with ones.

2fill in blank

medium

Complete the code to create a 2x3 array filled with ones.

NumPy

import numpy as np
array = np.ones([1])
print(array)

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

A(3, 2)

B(2, 3)

C[2, 3]

D[3, 2]

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping rows and columns in the shape tuple.

Using a list instead of a tuple for the shape.

The shape argument for a 2 rows and 3 columns array is (2, 3).

3fill in blank

hard

Fix the error in the code to create a 3x3 array of ones with integer type.

NumPy

import numpy as np
array = np.ones((3, 3), dtype=[1])
print(array)

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

Aint

B'float'

C'int'

Dinteger

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'integer' which is not a valid dtype string.

The dtype argument expects a string like 'int' to specify integer type.

4fill in blank

hard

Fill both blanks to create a 4x4 array of ones with float type and print its shape.

NumPy

import numpy as np
array = np.ones([1], dtype=[2])
print(array.shape)

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

A(4, 4)

B'float'

C'int'

D(4,)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a one-dimensional shape like (4,) instead of (4, 4).

Using 'int' instead of 'float' for dtype.

The shape should be (4, 4) for a 4x4 array, and dtype 'float' specifies floating point numbers.

5fill in blank

hard

Fill all three blanks to create a 2x5 array of ones with integer type and print the array.

NumPy

import numpy as np
array = np.ones([1], dtype=[2])
print([3])

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

A(2, 5)

B'int'

Carray

D'float'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'float' instead of 'int' for dtype.

Printing a wrong variable name.

The shape is (2, 5), dtype is 'int' for integers, and printing the variable array shows the result.

Practice

1. What does the np.ones() function do in NumPy?

easy

A. Creates an array filled with ones

B. Creates an array filled with zeros

C. Creates an array filled with random numbers

D. Creates an empty array

Solution

1. Step 1: Understand the function purpose

   np.ones() is designed to create arrays filled with the number one.

2. Step 2: Compare with other array creation functions

   Functions like np.zeros() create arrays filled with zeros, but np.ones() specifically fills with ones.

3. Final Answer:

   Creates an array filled with ones -> Option A

4. Quick Check:

   np.ones() = array of ones [OK]

Hint: Remember: ones means all elements are 1 [OK]

Common Mistakes:

• Confusing np.ones() with np.zeros()
• Thinking it creates random values
• Assuming it creates an empty array

2. Which of the following is the correct syntax to create a 2x3 array of ones with integer type using np.ones()?

easy

A. np.ones((2, 3), dtype=int)

B. np.ones([2, 3], type=int)

C. np.ones(2, 3, dtype='int')

D. np.ones(2, 3, int)

Solution

1. Step 1: Check the shape argument format

   The shape must be given as a tuple, so (2, 3) is correct.

2. Step 2: Check the dtype argument syntax

   The correct keyword is dtype, and the value can be int or 'int'.

3. Final Answer:

   np.ones((2, 3), dtype=int) -> Option A

4. Quick Check:

   Shape as tuple and dtype keyword correct [OK]

Hint: Use tuple for shape and 'dtype' keyword [OK]

Common Mistakes:

• Using list instead of tuple for shape
• Using 'type' instead of 'dtype'
• Passing shape as separate arguments

3. What is the output of the following code?

import numpy as np
arr = np.ones((2, 2), dtype=float)
print(arr)

medium

A. [[1 1]
[1 1]]

B. [[1. 1.]
[1. 1.]]

C. [[1 1 1]
[1 1 1]]

D. [[0. 0.]
[0. 0.]]

Solution

1. Step 1: Understand the shape and dtype

   The shape is (2, 2), so the array has 2 rows and 2 columns. The dtype is float, so elements are floats.

2. Step 2: Predict the printed output

   Each element is 1.0, printed as 1. with a decimal point. So the output is a 2x2 array of 1.0 values.

3. Final Answer:

   [[1. 1.] [1. 1.]] -> Option B

4. Quick Check:

   Shape (2,2) and float type means 1.0 values [OK]

Hint: Float dtype shows decimal points in output [OK]

Common Mistakes:

• Confusing integer and float output formats
• Misreading shape as (2,3)
• Expecting zeros instead of ones

4. Identify the error in this code snippet:

import numpy as np
arr = np.ones(3, 4)
print(arr)

medium

A. print() cannot display numpy arrays

B. Missing dtype argument

C. np.ones() cannot create 2D arrays

D. Shape must be a tuple, so use np.ones((3, 4))

Solution

1. Step 1: Check the shape argument

   The code passes two separate arguments 3 and 4, but np.ones() expects a single shape argument as a tuple.

2. Step 2: Correct the shape argument

   Use np.ones((3, 4)) to create a 3 by 4 array of ones.

3. Final Answer:

   Shape must be a tuple, so use np.ones((3, 4)) -> Option D

4. Quick Check:

   Shape argument must be tuple [OK]

Hint: Shape is always a tuple in np.ones() [OK]

Common Mistakes:

• Passing shape as separate arguments
• Forgetting parentheses around shape tuple
• Thinking dtype is mandatory

5. You want to create a 3D mask array of shape (2, 3, 4) filled with ones of boolean type using np.ones(). Which code snippet correctly does this?

hard

A. np.ones((2, 3, 4), type=bool)

B. np.ones([2, 3, 4], type=bool)

C. np.ones((2, 3, 4), dtype=bool)

D. np.ones(2, 3, 4, dtype=bool)

Solution

1. Step 1: Confirm the shape argument format

   The shape must be a tuple (2, 3, 4) to create a 3D array.

2. Step 2: Use correct dtype keyword and value

   The dtype keyword must be dtype and the value bool to create a boolean array.

3. Final Answer:

   np.ones((2, 3, 4), dtype=bool) -> Option C

4. Quick Check:

   Tuple shape and dtype=bool correct [OK]

Hint: Use tuple shape and dtype=bool for boolean arrays [OK]

Common Mistakes:

• Using list instead of tuple for shape
• Using 'type' instead of 'dtype'
• Passing shape as separate arguments