Python – Filter Similar Case Strings

When it is required to filter similar case strings, list comprehension can be used along with isupper() and islower() methods. This technique helps identify strings that are either completely uppercase or completely lowercase, filtering out mixed-case strings.

Example

Below is a demonstration of filtering strings with consistent casing ?

my_list = ["Python", "good", "FOr", "few", "CODERS"]

print("The list is :")
print(my_list)

my_result = [sub for sub in my_list if sub.islower() or sub.isupper()]

print("The strings with same case are :")
print(my_result)

Output

The list is :
['Python', 'good', 'FOr', 'few', 'CODERS']
The strings with same case are :
['good', 'few', 'CODERS']

How It Works

The list comprehension iterates through each string and applies two conditions:

• sub.islower() − Returns True if all alphabetic characters are lowercase
• sub.isupper() − Returns True if all alphabetic characters are uppercase
• The or operator includes strings that satisfy either condition

Alternative Approach Using Filter

You can also use the filter() function for the same result ?

my_list = ["Python", "good", "FOr", "few", "CODERS"]

my_result = list(filter(lambda x: x.islower() or x.isupper(), my_list))

print("The strings with same case are :")
print(my_result)

The strings with same case are :
['good', 'few', 'CODERS']

Key Points

• Mixed-case strings like "Python" and "FOr" are filtered out
• islower() and isupper() only check alphabetic characters
• Strings with numbers or symbols follow special rules for case checking

Conclusion

Use list comprehension with islower() or isupper() to filter strings with consistent casing. This approach effectively separates mixed-case strings from those with uniform letter casing.