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Python String islower() method

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  • Difficulty Level : Expert
  • Last Updated : 12 Aug, 2021

Python String islower() method checks if all characters in the string are lowercase. This method returns True if all alphabets in a string are lowercase alphabets. If the string contains at least one uppercase alphabet, it returns False.






  • True: If all the letters in the string are in lower case and
  • False: If even one of them is in upper case.

Example 1: Demonstrating the working of islower() 


# Python3 code to demonstrate
# working of islower()
# initializing string
islow_str = "geeksforgeeks"
not_islow = "Geeksforgeeks"
# checking which string is
# completely lower
print ("Is geeksforgeeks full lower ? : " + str(islow_str.islower()))
print ("Is Geeksforgeeks full lower ? : " + str(not_islow.islower()))


Is geeksforgeeks full lower ? : True
Is Geeksforgeeks full lower ? : False

Example 2: Practical Application

This function can be used in many ways and has many practical applications. One such application is checking for lower cases, checking proper nouns, checking for correctness of sentences that requires all lower cases. Demonstrated below is a small example showing the application of islower() method.


# Python3 code to demonstrate
# application of islower() method
# checking for proper nouns.
# nouns which start with capital letter
test_str = "Geeksforgeeks is most rated Computer \
            Science portal and is highly recommended"
# splitting string
list_str = test_str.split()
count = 0
# counting lower cases
for i in list_str:
    if (i.islower()):
        count = count + 1
# printing proper nouns count
print ("Number of proper nouns in this sentence is : "
                            + str(len(list_str)-count))


Number of proper nouns in this sentence is : 3

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