Python islower() built-in function is developed for handling specific string operations. The string method in Python islower() determines if all of the string’s case-based characters (letters) are lowercase. The Python islower() function is used to determine whether a string contains lowercase letters. Let us dig deep and understand more about Python’s islower() string class function along with examples.
Definition
- The Python islower() function returns True if all of the alphabets in the string are lowercase and if the string contains at least one capital alphabet, it returns False.
- If all the characters in a string are lowercase, the Python islower() string function returns True; otherwise, it returns False.
islower() Syntax
The islower() method is a built-in string handling function. Python islower() follows the below syntax method:
string.islower()
islower() Parameters
The islower() function does not accept any parameters. If any parameters are passed, an error will be generated.
Return value of islower()
Python’s string islower() function is responsible for returning a Boolean value:
- True – if all the alphabets in the string are of lowercase
- False – if the string contains at least one alphabet which is in uppercase state
Note – The islower() function always returns False if the given string contains only symbols or numbers. If there is at least one alphabet along with symbols and numbers, then the function checks the condition and returns True or False accordingly.
Example 1: Return value from islower()
Example
# Python program to illustrate islower()
# contains all lowercase characters
txt = 'what a lovely day'
print(txt.islower())
# contains uppercase as well as lowercase characters
txt = 'What a Lovely Day'
print(txt.islower())
# contains numbers and lowercase characters
txt = '1 am g00d'
print(txt.islower())
# contains only symbols and numbers
txt = '138$^#'
print(txt.islower())
# empty string
txt = ' '
print(txt.islower())
Output
True
False
True
False
False
Example 2: How to use islower() in a program?
Example
# Python program to illustrate islower() in real-life applications
txt = 'this is a nice place to camp'
if txt.islower() == True:
   print('Does not contain any uppercase letters')
else:
   print('Contains uppercase letters')
txt = 'I have a pet dog'
if txt.islower() == True:
   print('Does not contain any uppercase letters')
else:
   print('Contains uppercase letters')
Output
Does not contain any uppercase letters
Contains uppercase letters
Errors and Exceptions while using islower()
- Python islower() returns “True” for whitespaces, but returns “False” if the string contains only whitespace.
- As the islower() function does not accept any arguments, it returns an error if a parameter is passed.
- If the string contains digits and symbols along with characters, then it returns “True”, but if the string contains only numbers and digits, it returns “False”.
Frequently Asked Questions
Q1. What does islower() do in Python?
Python islower() built-in function is developed for handling specific string operations. The string method in Python islower() determines if all of the string’s case-based characters (letters) are lowercase. If all the characters in a string are lowercase, the Python islower() string function returns True; otherwise, it returns False.
Q2. Explain islower in Python along with examples?
The Python islower() function returns True if all of the alphabets in the string are lowercase and if the string contains at least one capital alphabet, it returns False. Python islower() follows the below syntax method:
string.islower()
Python’s string islower() function is responsible for returning a Boolean value:
- True – if all the alphabets in the string are of lowercase
- False – if the string contains at least one alphabet which is in uppercase state
Example
# Python program to illustrate islower()
# contains all lowercase characters
txt = 'hello everyone'
print(txt.islower())
# contains uppercase as well as lowercase characters
txt = 'Good Morning Everyone'
print(txt.islower())
# contains numbers and lowercase characters
txt = '12sdfjb543'
print(txt.islower())
# contains only symbols and numbers
txt = '0315&*!$279'
print(txt.islower())
# empty string
txt = ' '
print(txt.islower())
Output
True
False
True
False
False
Q3. How do you capitalize all letters in Python?
When working with a string in Python, you may want to convert the string to uppercase or check if the string is already in uppercase. This is where the Python upper() method comes into play. The upper() function in Python changes all the lowercase characters in a string to uppercase and returns the resulting string.
Syntax:
string.upper()
Example
# Python program to illustrate upper()
# string with all lowercase letters
txt = 'hello everyone'
print(txt.upper())
# string with numbers
txt = 'Hello Everyone. H0w a3e you a11'
print(txt.upper())
Output
HELLO EVERYONE
HELLO EVERYONE. H0W A3E YOU A11
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