Python String islower() method

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.

Python String islower() Method Syntax

Syntax:  string.islower()

Returns: 

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

Python String islower() Method Example

Python3

print("geeks".islower())

Output:

True

Example 1: Demonstrating the working of islower() 

Python3

# initializing string
islow_str = "geeksforgeeks"
not_islow = "Geeksforgeeks"

# checking which string is
# completely lower
print ("Is", islow_str, "full lower ? : " + str(islow_str.islower()))
print ("Is", not_islow, "full lower ? : " + str(not_islow.islower()))

Output:

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 Python islower() method.

Python3

# 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))

Output:

Number of proper nouns in this sentence is : 3