Modifying and Deleting Strings

Modifying and Deleting Strings

As you already learnt, strings in python are immutable. That means, once you define a string modifications or deletion is not allowed. If you want to modify the string, a new string value can be assign to the existing string variable.

Example

>>>str1="How are you"

>>>str1[0]="A"

Traceback (most recent call last):

File "<pyshell#1>", line 1, in <module>

str1[0]="A"

TypeError: 'str' object does not support item assignment

In the above example, string variable str1 has been assigned with the string “How are you” in statement 1. In the next statement, we try to update the first character of the string with character ‘A’. But python will not allow the update and it shows a TypeError.

To overcome this problem, you can define a new string value to the existing string variable. Python completely overwrite new string on the existing string.

Example

>>>str1="How are you"

>>>print (str1)

How are you

>>>str1="How about you"

>>>print (str1)

How about you

Usually python does not support any modification in its strings. But, it provides a function replace() to change all occurrences of a particular character in a string.

General formate of replace function:

replace(“char1”, “char2”)

The replace function replaces all occurrences of char1 with char2.

Example

>>>str1="How are you"

>>>print (str1)

How are you

>>>print (str1.replace("o", "e"))

Hew are yeu

Similar as modification, python will not allow deleting a particular character in a string.

Whereas you can remove entire string variable using del command.

Example: Code lines to delete a particular character in a string:

>>>str1="How are you"

>>>del str1[2]

Traceback (most recent call last):

File "<pyshell#7>", line 1, in <module>

del str1[2]

TypeError: 'str' object doesn't support item deletion

Example: Code lines to delete a string variable

>>>str1="How about you"

>>>print (str1)

How about you

>>>del str1

>>>print (str1)

Traceback (most recent call last):

File "<pyshell#14>", line 1, in <module>

print (str1)

NameError: name 'str1' is not defined