String Interpolation is the process of substituting values of variables into placeholders in a string. Let’s consider an example to understand it better, suppose you want to change the value of the string every time you print the string like you want to print “hello <name> welcome to Lazyroar for Lazyroar” where the <name> is the placeholder for the name of the user. Instead of creating a new string every time, string interpolation in Python can help you to change the placeholder with the name of the user dynamically. 

Python String Interpolation

% – Formatting

% – Formatting is a feature provided by Python that can be accessed with a % operator. This is similar to the printf style function in C.

Example: Formatting string using the % operator

Welcome to Lazyroar
Hello ! This is Lazyroar.

Let’s say it’s just a complicated version. Still, we can use it if we have a lot of variables to get substituted in the string as we don’t always want to use(“string” + variable + “string” + variable + variable + “string”) this representation. So for this purpose, we can go with %-formatting.

Note: To know more about %-formatting, refer to String Formatting in Python using %

Str.format()

str.format() works by putting in one or more replacement fields and placeholders defined by a pair of curly braces { } into a string. The value we wish to put into the placeholders and concatenate with the string passed as parameters into the format function. 

Example: Formatting strings using the format() method.

Hello, Lazyroar

We can also use the variable name inside the curly braces {}. This will allow us to use the parameters of format functions in any order we want.

Example: Format functions with variables inside curly braces.

Hello! This is GeeksForGeeks.
GeeksForGeeks! This is Hello.

Note: To know more about str.format(), refer to format() function in Python

f-strings

PEP 498 introduced a new string formatting mechanism known as Literal String Interpolation or more commonly as F-strings (because of the leading f character preceding the string literal). The idea behind f-strings is to make string interpolation simpler. 

To create an f-string, prefix the string with the letter “ f ”. The string itself can be formatted in much the same way that you would with str. format(). F-strings provide a concise and convenient way to embed Python expressions inside string literals for formatting.

Example: Formatting Strings using f-strings

Hello! This is Lazyroar
(2 * 3)-10 = -4

We can also use f-strings to calculate some arithmetic operations and it will perform the inline arithmetic. See the below example – 

Example: Inline arithmetic using f-strings

(2 * 3)-10 = -4

Note: To know more about f-strings, refer to f-strings in Python

String Template Class

In the String module, Template Class allows us to create simplified syntax for output specification. The format uses placeholder names formed by $ with valid Python identifiers (alphanumeric characters and underscores). Surrounding the placeholder with braces allows it to be followed by more alphanumeric letters with no intervening spaces. Writing $$ creates a single escaped $:

Example: Formatting string using Template Class

Hello ! This is Lazyroar.

Note: To know more about the String Template class, refer to String Template Class in Python