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The upper() string method is used to convert only the all the lowercase characters in a string to upper 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 upper()

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

# Signature of upper() method 
upper()

Calling upper() method on a string object.




# Python - Method upper() Example



# Creating a string
s1 = ('Czech Republic')


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


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





Output




Value of string : Czech Republic
Calling the upper() method  on string : CZECH REPUBLIC


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






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


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


Let's show you this by an example -:
Here in program below, we have initialized a string object with a value Pluto - A dwarf planet and we are trying to upper case all of its lower case characters by calling the upper() method on it.



# Python - Method upper() Example



# Creating a string
s1 = ('Pluto - A dwarf planet')

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


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


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





Output is :




String's value : Pluto - A dwarf planet
Calling the upper() method : PLUTO - A DWARF PLANET
Original string after calling upper() - Pluto : A dwarf planet


Even after calling the method upper() on the string object, the original case of its content remains the same - Pluto - A dwarf planet, because the method upper() only returns a new string with all its characters in upper case letter, without changing the original invoked string.




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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 upper() method on the original object, we can make the reference variable to the original string, point to the result of calling the upper() method(but in this case, the original string will be lost).



# Python - upper() method example.



# Creating a string
s = 'you have got to live your life!'


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


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


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





Output is :




Original string value :  you have got to live your life!
String value after upper() :  YOU HAVE GOT TO LIVE YOUR LIFE!








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