Python program to extract uppercase letters

Last update on March 31 2025 12:55:52 (UTC/GMT +8 hours)

2. Uppercase Extractor

Write a Python program that uses the filter function to extract all uppercase letters from a list of mixed-case strings.

Sample Solution:

Python Code:

# Define a list of mixed-case strings
mixed_case_strings = ["Hello", "w3resource", "Python", "Filter", "Learning"]

print("Original list of strings:\n",mixed_case_strings)
# Use the filter function to extract uppercase letters
uppercase_letters = list(filter(lambda char: char.isupper(), ''.join(mixed_case_strings)))

print("\nExtract all uppercase letters from the said list of mixed-case strings:")
# Print the extracted uppercase letters
print(uppercase_letters)

Explanation:

In the exercise above,

• First, start with a list of mixed-case strings named mixed_case_strings.
• Next, we use the filter function to filter characters from all strings and retain only uppercase letters. We do this by using a lambda function that checks if a character is uppercase using the isupper() method.
• The filter function returns an iterable of uppercase letters, which we convert to a list.
• Finally, we print the extracted uppercase letters.

Sample Output:

Original list of strings:
 ['Hello', 'w3resource', 'Python', 'Filter', 'Learning']

Extract all uppercase letters from the said list of mixed-case strings:
['H', 'P', 'F', 'L']

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python function that filters out only the uppercase characters from each string in a list and returns a list of strings containing just the uppercase letters.
• Write a Python program that applies the filter function on a single mixed-case string to extract all uppercase letters and then joins them into a new string.
• Write a Python program to filter a list of strings, keeping only those strings that are entirely in uppercase using the filter function.
• Write a Python function that uses filter to extract uppercase letters from each element of a list and then counts the total number of uppercase characters.

Python Code Editor:

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