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The lower() string method is used to convert only the all the lowercase characters in a string to lower case letters.

Note : None of the string methods change the original string and only return a new string which reflects the change performed by the string method, hence the returned string must be stored or used(if needed to reflect the result), otherwise it is lost.

Signature of lower()

The lower() method has no parameters, so we don't have to worry about passing it some value.

# Signature of lower() method 
lower()

Calling lower() method on a string object.




# Python - Method lower() Example



# Creating a string
s1 = ('KING KONG IS COMING!')


# Printing the original string
print('Value of string  : ', s1)


# Calling  the lower() method on string object 
print('Calling the lower() method  on string : ', s1.lower())





Output




Value of string : KING KONG IS COMING!
Calling the lower() method  on string : king kong is coming


A string object was initialized to a value KING KONG IS COMING!. When the method lower() was called on this string object, it returned a string with all its upper case characters changed to lower case letters.




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Method lower() does not modify the original characters in a string object


The method lower() does not modify the original string, but, it only returns a transformed version of the invoked string with all its upper case characters changed to lower case characters.


Let's show you this by an example -:
Here in program below, we have initialized a string object with a value Jupiter - The Biggest Planet of our Solar System and we are trying to lower case all of its lower case characters by calling the lower() method on it.



# Python - Method lower() Example



# Creating a string
s1 = ('Jupiter - The Biggest Planet of our Solar System')

# Printing the original string
print('Original string  before calling lower() : ', s1)


# Calling  the lower() method on string object 
print('Calling the lower() method : ', s1.lower())


# Printing the original string
print('Original string after calling lower() : ',  s1)





Output is :




String's value : Jupiter - The Biggest Planet of our Solar System
Calling the lower() method : jupiter - the biggest planet of our solar system
Original string after calling lower() - Jupiter - The Biggest Planet of our Solar System


Even after calling the method lower() on the string object, the original case of its content remains the same - Jupiter - The Biggest Planet of our Solar System, because the method lower() only returns a new string with all its characters in lower case letter, without changing the original invoked string.






Strings are immutable but reference variables are mutable.


String objects are immutable, but the reference variables pointing to them are not, therefore in order to display the impact of calling the lower() method on the original object, we can make the reference variable to the original string, point to the result of calling the lower() method(but in this case, the original string will be lost).



# Python - lower() method example.



# Creating a string
s = 'C\'mon, get up and fight!'


# Printing the original string
print('Original string is : ', s)


# Result of calling lower() is made to reference by the reference of original string.
s= s.lower()


# Old reference variable pointing to the new string
print('String value after lower()  : ', s)





Output is :




Original string value :  C'mon get up and fight!
String value after lower() :  c'mon get up and fight!








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String islower() Method >



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