NumPy: Test digits only, lower case and upper case letters only

Last update on April 29 2025 12:55:19 (UTC/GMT +8 hours)

17. Check String Composition: Digits, Lowercase, Uppercase

Write a NumPy program to check whether each element of a given array is composed of digits only, lower case letters only and upper case letters only.

Sample Solution:

Python Code:

# Importing necessary library
import numpy as np

# Creating a NumPy array containing strings
x = np.array(['Python', 'PHP', 'JS', 'Examples', 'html5', '5'], dtype=np.str)

# Displaying the content of the original array
print("\nOriginal Array:")
print(x)

# Checking if each element contains digits only
r1 = np.char.isdigit(x)

# Checking if each element contains lower case letters only
r2 = np.char.islower(x)

# Checking if each element contains upper case letters only
r3 = np.char.isupper(x)

# Displaying results
print("Digits only =", r1)
print("Lower cases only =", r2)
print("Upper cases only =", r3)

Sample Input:

(['Python', 'PHP', 'JS', 'Examples', 'html5', '5'], dtype=np.str)

Sample Output:

Original Array:
['Python' 'PHP' 'JS' 'Examples' 'html5' '5']
Digits only = [False False False False False  True]
Lower cases only = [False False False False  True False]
Upper cases only = [False  True  True False False False]

Explanation:

In the above exercise –

x = np.array(['Python', 'PHP', 'JS', 'Examples', 'html5', '5'], dtype=np.str): This statement creates a NumPy array x containing 6 strings with different characters and cases.

r1 = np.char.isdigit(x): This statement creates a boolean NumPy array r1 of the same shape as x with True where each element of x is a digit and False otherwise.

r2 = np.char.islower(x): This statement creates a boolean NumPy array r2 of the same shape as x with True where each element of x is in lowercase and False otherwise.

r3 = np.char.isupper(x): This statement creates a boolean NumPy array r3 of the same shape as x with True where each element of x is in uppercase and False otherwise.

Pictorial Presentation:

NumPy String: Test digits only, lower case and upper case letters only

For more Practice: Solve these Related Problems:

Create a function that checks if each string in an array is composed entirely of digits using np.char.isdigit.
Implement a solution that verifies if each element is all lowercase using np.char.islower and all uppercase using np.char.isupper.
Test the function on an array of mixed content and return separate boolean arrays for each condition.
Combine the results into a structured output that maps each string to its composition characteristics.

Go to:

Previous: Write a NumPy program to count the lowest index of "P" in a given array, element-wise.
Next: Write a NumPy program to check whether each element of a given array starts with "P".

Python-Numpy Code Editor:

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